OBC VOLUME 2 · SUPPLEMENTARY STANDARD SB-4Updated for the 2024 Ontario Building Code
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SB-4 — Measures for Fire Safety in High Buildings
Supplementary Standard SB-4 ("Measures for Fire Safety in High Buildings") forms part of Volume 2 of the 2024 Ontario Building Code. The full text is reproduced below with a linked table of contents.
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2024MMAH Supplementary Standard SB-4
SB-4 Measures for Fire Safety
in High Buildings
(This Supplementary Standard is based in large measure on the Supplement to the National Building Code of Canada 1990
and the Appendix Notes to Subsection 3.2.6. of the National Building Code of Canada 2020)
Introduction
Experience with high buildings has shown that the time required for complete evacuation can exceed that which is
considered necessary for the safe egress of all occupants. Studies of the "chimney effect" and observations of smoke
movement in actual fires have shown that fire compartmentation to contain a fire on any storey will not usually prevent the
movement of smoke through elevator, stair and other vertical shafts to the upper floors of a high building. Occupants of a
high building in which an automatic sprinklers are not installed, and particularly those on upper storeys, could be faced
with severe smoke conditions from fires occurring in storeys below them before their own evacuation is possible. The
requirements in Section 3.2.6. of Division B in the Building Code are intended to maintain safe conditions for occupants of
a high building who may have to remain in the building during a fire, and to assist the firefighters by providing efficient
access to the fire floor.
This Supplementary Standard is intended to assist a designer in complying with the requirements of Subsection 3.2.6. of
Division B of the Code. The knowledge requirements are well within the capabilities of a competent designer. The
designer should acknowledge however, that successful application requires a clear understanding of the principles that
govern smoke movement. Subsection 3.2.6. contains only those items that relate to the design and construction of a
building while the operation of the facilities and recommended actions to be taken by the building owner, building
occupants and fire department are covered by the Fire Code.
Application of SB-4: Design of New Buildings and Renovations to Existing Buildings
Section 1: Section 1 of this standard, describes compliance with the requirements of Subsection 3.2.6. of Division B of the
Code and is applicable to both new and existing buildings. The Code user should review the provisions contained in
Section 1 with the corresponding provisions in Subsection 3.2.6. of Division B and determine the applicability of each.
Provision [3.2.6.2.(1)] is applicable to the renovation of existing buildings that are sprinklered. Provision [3.2.6.2.(7)] is
specifically applicable to the renovation of existing buildings that are not sprinklered.
Section 2: Section 2 of this standard summarizes smoke control measures applicable to certain common building designs.
Compliance with one of these measures is considered to meet the requirements of the code for smoke control in existing
buildings.
Section 3: Section 3 further details the measures that are referenced in Section 2 and can be utilized to achieve the
strategies described in Section 2.
Smoke Control in High Buildings
The designer is cautioned that the tabular and graphical information in this standard was developed for buildings having
conventional configurations. The designer has to judge the extent to which the building under consideration has
characteristics that will allow the application of this information; this is particularly true of designs employing air-handling
systems for which a realistic assessment of the leakage characteristics of the enclosures of spaces may be critical.
2024MMAH Supplementary Standard SB-4
It is assumed that buildings regulated by Subsection 3.2.6. of Division B will be in an area served by a fire department
capable of an early response and that all firefighting and rescue situations will be under the direct control of the officer in
charge of the fire department responding to the emergency. It is important that firefighters be provided with a smoke free
access to fire floors below grade. Provisions are included to separate exit stairways serving storeys above grade from those
serving storeys below grade, and to limit entry of smoke into these shafts. Similarly, elevator hoistways and service shafts
are required to be provided with a separation near grade, or be designed to limit their functioning as paths of smoke
movement into upper floor areas from storeys below grade.
It is assumed that in the event of fire, occupants of the floor on which the fire occurs will leave by exit stairs immediately
following the sounding of a fire alarm, and that occupants of the floor immediately above the floor on which the fire occurs
will be advised to leave by the first fire department officer on the scene or other person assigned this responsibility.
Occupants of all other floors may remain on their floors unless otherwise directed. It is also assumed that the owner of the
building has complied with the Emergency Planning Section of the Fire Code by preparing a comprehensive fire safety
plan to safeguard the building occupants and that the building supervisory staff are familiar with the requirements of
Subsection 3.2.6. of Division B and with their responsibilities under the fire safety plan.
It is further assumed that the cumulative population of storeys below grade divided by 1.8 times the width in metres of all
exit stairs at the storey under consideration will not exceed the 300 limit referred to in Article 3.2.6.1. of Division B, and
that occupants of storeys below grade will evacuate the building by the stair shafts immediately after the discovery of a fire
in a storey below grade.
The Building Code requires that a check be made of the smoke control system when requested by the authority having
jurisdiction in accordance with the procedures described in Appendix C of this Supplementary Standard. This check will
indicate deficiencies caused by inexact estimates of the leakage characteristics or of air supply requirements and, in all but
the most extreme cases, will provide an opportunity for appropriate adjustments before the system is put into service.
Section 1 Building Code Provisions
[3.2.6.2.(1)] Limits to Smoke Movement in New and Existing Buildings that are
Sprinklered
(1) A new or an existing building that is sprinklered and is required to conform to the provisions of Subsection 3.2.6. of
Division B shall be designed in accordance with Sentences 3.2.6.2.(2) to (5) and this Supplementary Standard to limit the
danger to occupants and firefighters from exposure to smoke in a building fire.
(2) Except as required in Sentence (1), where smoke control system of an existing sprinklered building is materially
altered, the altered portions of the system shall meet the requirements of Sentences 3.2.6.2.(2) to (5) and this
Supplementary Standard to limit the danger to occupants and firefighters from exposure to smoke in a building fire.
Electrical Sprinkler Supervision
(3) The sprinkler system is equipped with a water flow and supervisory signal system that will,
(a) transmit automatically a waterflow signal directly to the fire department, or through an independent central station,
(b) transmit automatically other supervisory signals to a proprietary control centre or to an independent central station,
and
(c) actuate a signal at the central alarm and control facility described in Article 3.2.6.7. of Division B.
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2024MMAH Supplementary Standard SB-4
[3.2.6.2.(2)] Stairway Protection Below Lowest Exit Level
These provisions are intended to apply to common building designs. Where a stair serving floors below the lowest exit
level is open to the exterior or the stair serves only one storey below grade, compliance with the following provisions may
not be necessary.
A stairway serving floors below the lowest exit level is considered to comply with the intent of Sentence 3.2.6.2.(2) of
Division B if all of the following conditions are satisfied.
(1) The stairway has a vent or door to the outdoors at or near the top of the stair shaft that has an openable area of not
less than 0.1 m2 for each storey served by the stairway, less 0.01 m 2 for each weatherstripped door and 0.02 m2 for each
door that is not weatherstripped opening into the stairway.
(2) The stairway is enclosed in a shaft that
(a) does not pass through the floor above the lowest exit level and is separate from a shaft that contains a stairway
serving upper storeys, or
(b) contains a stairway serving upper storeys, but is separated from that stairway at the lowest exit level by a fire
separation having a fire resistance rating not less than that required for the shaft enclosure.
(3) The stairway is provided with equipment capable of maintaining a flow of air introduced at or near the bottom of the
stair shaft, at a rate equal to 0.47 m3/s for each storey served by the stairway.
[3.2.6.2.(3)] Requirements for Stair Shafts Serving Storeys Above Lowest Exit
Level
Open doors and vents at the bottom of a stair shaft that serve storeys above the lowest exit level, will create a positive
pressure in the shaft relative to adjacent floor areas and thus prevent smoke infiltration into the shaft. This pressure
differential, created as a result of the stack effect will be the greatest during the winter, when the difference in temperature
between the interior and the exterior of the building is most pronounced. If a stair shaft does not have a direct opening to
the exterior, alternative means must be provided to achieve the pressure differential and consequent smoke control. In the
instance where a corridor or vestibule is used as a link between the exit level of an interior stair shaft and the outdoors, it
will be necessary to assess the reliability and performance of the overall system in creating the necessary stairway
pressurization. The probability of all doors or closures being opened at the same time, as well as the size of the vestibule
and its impact on the overall smoke control system, are factors that need to be considered.
(1) Each stairway that serves storeys above the lowest exit level shall have a vent to the outdoors, at or near the bottom
of the stair shaft, that,
(a) has an openable area of 0.05 m2 for every door between the stair shaft and a floor area, but not less than 1.8 m2,
(b) opens directly to the outdoors or into a vestibule that has a similar opening to the outdoors, and
(c) has a door or closure that,
(i) is openable manually, and
(ii) can remain in the open position during a fire emergency.
If mechanical methods are used to develop a positive pressure in a stair shaft, a minimum pressure differential of 12 Pa is
recommended to prevent smoke migration from floor areas in a sprinklered building where fire temperatures are controlled
and smoke movement may be dominated by stack effect in a stair shaft. During a fire emergency, persons will be entering
and exiting a stair shaft as they move to a place of safety and under these conditions the number of doors open to the stair
shaft cannot be predetermined. The number will vary depending on the occupancy of the building, population density and
the evacuation plan for the building. It should be assumed that two doors are open. This is based in part as a practical level
for most buildings and considers the positive fire experience in sprinklered buildings.
2024MMAH Supplementary Standard SB-4
The maximum pressure differential created by a mechanical system should not prevent doors to the stair shafts from being
opened. A specific maximum value cannot be given, as this value will depend on the door opening force and size of the
door. These values should be calculated for each specific case. A maximum value of 130 N is suggested by research as the
force that can be opened by the majority of people in most occupancies, however this value is above the maximum value of
90 N generally specified in this Code (Section 3.4. of Division B). The use of values below 130 N can create a practical
problem in achieving effective smoke control as it is difficult to design for the acceptable minimum and maximum pressure
differential range. Special consideration may need to be given to doors located in a barrier free path of travel.
Care should be taken by designers and by building and fire officials in implementation of these requirements. Assumptions
involved in the design of a smoke control system may be different from final construction conditions. For this reason each
system should be tested after installation to ensure that the design intent is met. The minimum pressure differential is not
intended to apply to locations in stair shafts when nearby doors are open to adjacent floor areas.
[3.2.6.2.(4)] Limiting Smoke Movement into Storeys Above Lowest Exit Level.
Measures to prevent the migration of smoke from floor areas below the lowest exit storey into upper storeys include the
following.
(1) An elevator hoistway that passes through the floor above the lowest exit storey should not penetrate the floor of the
storey immediately below the lowest exit storey, unless there is a vestibule between the shaft and each floor area below
the lowest exit storey that
(a) has a fire separation, with a fire resistance rating not less than 45 min, between the vestibule and any public corridor,
(b) has a fire separation, with a fire resistance rating not less than that required for an exit by Article 3.4.4.1. of
Division B, between the vestibule and any stair or elevator enclosure or any part of a floor area, other than a public
corridor, and
(c) except for elevator hoistway entrances, has a self-closing device on any door through the fire separation required by
Clauses (a) and (b), with the door opening in the direction of travel from the floor area to the exit stairway.
(2) A vertical service space, other than an elevator hoistway, that passes through the floor assembly above the lowest
exit storey, should be provided with a tight fitting noncombustible seal or fire stop at the floor assembly of the storey
immediately below the lowest exit storey, unless
(a) the vertical service space is vented to the outdoors at the top and the vent has an openable area that is not less than
(i) that obtained from Graph 1 in Appendix A to SB-4 if the vertical service space is in a building in which other
shafts are not mechanically pressurized, or
(ii) that obtained from Graph 2 in Appendix A to SB-4 if the vertical service space is in a building in which other
shafts are mechanically pressurized,
(b) for a shaft that serves floor areas above the lowest exit storey, a vent is located
(i) at or near the top of the shaft if the shaft is above the mid height of the building, or
(ii) at or near the foot of the shaft at or near the exit level if the top of the shaft is below the mid height of the
building, or
(c) for a shaft that serves floor areas below the lowest exit storey, a vent is located at or near the top of the shaft.
(3) Any closure provided for a vent opening referred to in Sentence (2) must be openable:
(a) manually,
(b) on a signal from a smoke detector located at or near the top of the shaft, and
(c) by a control device located at the central alarm and control facility.
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2024MMAH Supplementary Standard SB-4
[3.2.6.2.(5)] Air Moving Fans
(1) Except for exhaust fans in kitchens, washrooms and bathrooms in dwelling units, and except for fans used for smoke
venting in Article 3.2.6.6. of Division B, air moving fans in a system that serves more than 2 storeys shall be designed
and installed so that in the event of a fire these fans can be stopped by means of a manually operated switch at the central
alarm and control facility.
Equivalent Measure
Where a building is designed in accordance with Measure A as described in Sections 2 and 3 of this Supplementary Standard,
the building shall be deemed to comply with Sentences 3.2.6.2.(2) to (5) of Division B of the Building Code.
[3.2.6.2.(7)] Limits to Smoke Movement in Existing Buildings that are Not
Sprinklered
(1) An existing building that is not sprinklered and that is governed by the provisions of Subsection 3.2.6. of Division B
shall be designed in accordance with Sentences (2) to (8) to limit the danger to occupants and firefighters from exposure
to smoke in a building fire.
Smoke Protection for Floor Areas
(2) Except as provided in Sentences (5) to (8), a building referred to in Sentence (1), shall be designed so that, during a
period of 2 h after the start of a fire, all floor areas that are above the lowest exit storey will not contain more than 1% by
volume of contaminated air from the fire floor, assuming an outdoor temperature equal to the January design temperature
on a 2.5% basis determined in conformance with Supplementary Standard SB-1.
Smoke Protection for Exit Stairs
(3) Except as provided in Sentences (7) and (8), a building referred to in Sentence (1), shall be designed so that during a
period of 2 h after the start of a fire, the limit described in Sentence (2) on the movement of contaminated air into other
floor areas is not exceeded in,
(a) each exit stair serving storeys above the lowest exit level, and
(b) each exit stair serving storeys below the lowest exit level.
Smoke Protection for Firefighters’ Elevators
(4) Except as provided in Sentence (7), a building referred to in Sentence (1), shall be designed so that during a period
of 2 h after the start of a fire, the limit described in Sentence (2) on the movement of contaminated air into other floor
areas is not exceeded in a shaft that contains an elevator for use by firefighters required by Article 3.2.6.5. of Division B.
Areas of Refuge
(5) In a building of Group C major occupancy classification, the requirements of Sentence (2) are waived where
occupants above the first storey can enter and be safely accommodated in floor areas or parts of floor areas that shall
(a) be designated and identified in the building as areas of refuge,
(b) be located on every storey except if the building is not more than 75 m, measured between grade and the floor level
of the top storey, on every fifth storey,
(c) provide not less than 0.5 m2 of floor space per ambulatory occupant and 1.5 m2 of floor space per non-ambulatory
occupant,
(d) have access corridors and doors leading to each designated part of a floor area on the same storey sufficient to
provide 3.67 mm of width for every person who may have to use these passages to reach the designated part of a
floor area,
2024MMAH Supplementary Standard SB-4
(e) have access stairs from intervening storeys leading to each designated part of a floor area sufficient to provide
5.5 mm of width for every person who may have to use these stairs to reach the designated part of a floor area, and
(f) not contain more than 1% by volume of contaminated air from the fire floor during a period of 2 h after the start of a
fire, assuming an outdoor temperature equal to the January design temperature on a 2.5% basis determined in
conformance with Supplementary Standard SB-1.
Lower Buildings
(6) The requirements of Sentence (2) are waived in a building of Group C major occupancy classification where,
(a) the building is not more than 75 m high measured between grade and the floor level of the top storey, and
(b) the number of occupants of storeys above grade is not more than 3.6 times the area in square metres of treads and
landings in the exit stairs serving these storeys.
Residential Buildings
(7) The requirements of Sentences (2) and (4) and Clause (3)(a) are waived in a building of Group C major occupancy
classification, where
(a) each suite above grade has direct access to an exterior balcony that conforms to the requirements of Sentence
3.3.1.7.(4) of Division B,
(b) each stairway that serves storeys above the lowest exit level is vented to the outdoors at or near the bottom of the
stair shaft,
(c) measures are taken to limit movement of smoke from a fire in a floor area below the lowest exit storey into upper
storeys, and
(d) where, except for exhaust fans in kitchens, washrooms and bathrooms in dwelling units, air moving fans are
designed and installed so that in the event of a fire such fans can be stopped by means of a manually operated switch
at the central alarm and control facility where the system serves more than 2 storeys.
(8) The requirements of Sentences (2) and (3) are waived in a Group C major occupancy apartment building.
[3.2.6.3.(1)] Connected Buildings
The measures described here are intended to prevent movement of smoke from one building to another where at least one
building is a high building. They are of particular significance for two buildings of unequal height that are joined together.
The measures suggested include the provision of a large opening to the outdoors in a connecting vestibule enabling smoke
entering through leakage areas around doors to be vented to the outdoors, or pressurization to maintain a higher pressure in
the vestibule than in adjacent spaces, as illustrated in Figures 17 to 19 in Section 2.
The provisions for protection of openings are described in terms applicable doorways, as this is expected to be the most
commonly occurring opening. Openings other than doorways should be avoided if possible. Openings should be protected
by an airlock that gives the at least the same level of protection as the vestibule described below.
The requirement of Article 3.2.6.3. of Division B limiting the movement of smoke from one building to another may be
met by incorporating in the link between the buildings the provisions of Sentences (1) and (2) described below.
(1) A firewall conforming to Subsection 3.1.10. of Division B is constructed between one building and the other with
any opening in the firewall protected against the passage of smoke by a vestibule that has
(a) a fire separation between the vestibule and a public corridor with a fire resistance rating not less than 45 min,
(b) a fire separation between the vestibule and the remainder of the floor area, other than a public corridor, with a fire
resistance rating not less than that required by Article 3.4.4.1. of Division B for an exit,
(c) a fire separation between the vestibule and a stair enclosure or elevator hoistway with a fire resistance rating not less
than that required by Article 3.4.4.1. of Division B for an exit, and
(d) any door in the fire separation required by Clauses (a), (b) or (c), except for an elevator entrance, provided with a
self-closing device as required by Article 3.1.8.13. of Division B and opening in the direction of travel from the
floor area to the exit stairway.
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2024MMAH Supplementary Standard SB-4
(2) The vestibule referred to in Sentence (1) should have
(a) a vent to the outdoors that has a net area of 10(0.023d + 0.00045a) m 2, where 'd' is the number of doors having a
perimeter not more than 6 m that open into the vestibule, or if the perimeter of doors exceeds 6 m, the value 'd' is
increased in direct proportion to the increase in the perimeter, and 'a' is the area in square metres of enclosing walls,
floors and ceilings whose outer face is in contact with the outside air, except that where the outer face of a wall is in
contact with the ground or fill, it is assumed that there is no leakage through that portion, and the value of 'a' is
assumed to be zero, or
(b) equipment capable of maintaining a supply of air into the vestibule sufficient to ensure that the air pressure in the
vestibule when the doors are closed is higher by at least 12 Pa than that in adjacent floor areas when the outdoor
temperature is equal to the January design temperature on a 2.5% basis.
[3.2.6.5.(6)(b)] Electrical Cable Protection
Electrical cables that provide continuous operation for 1 hour when subjected to the fire exposure/temperature curve of
CAN/ULC-S101-14, “Standard Methods of Fire Endurance Tests of Building Construction and Materials”, do not need
additional protection against exposure to fire.
[3.2.6.6.(1)] Venting to Aid Firefighting
(1) The requirements of Sentence 3.2.6.6.(1) of Division B and of Measures H or I are met by incorporating in a floor
area windows or wall panels as described in Sentence (2), by smoke shafts as described in Sentences (3) to (7) or by the
use of building exhaust systems as described in Sentence (8).
(2) Where windows or wall panels are used for venting as required in Sentence (1), they must
(a) be uniformly distributed along the exterior wall of each storey,
(b) have a total area of not less than one percent of the exterior wall area of each storey,
(c) be readily openable from the interior without the use of wrenches or keys,
(d) be readily identified from the interior, and from the exterior where they are accessible to firefighters, and
(e) be designed so that when opened they will not endanger persons outside the building during a fire.
(3) Where one or more smoke shafts or vertical service spaces are used for venting to meet the requirements of
Sentence (1), they must
(a) have an opening or openings into each storey with an aggregate area not less than that obtained from Table 1 for the
height of the shaft, the area of the largest floor area served by the smoke shaft and the leakage characteristics of the
shaft wall and closures obtained from Tables 2 and 3,
(b) have an aggregate unobstructed cross-sectional area equal to that provided in Clause (a), and
(c) be designed to comply with the requirements of Sentence (4).
(4) Each smoke shaft or vertical service space described in Sentence (3) must
(a) be separated from the remainder of the building by a fire separation that has a fire-resistance rating at least equal to
that required for the floor assembly through which it passes, or be designed as a chimney conforming to Part 6 of
Division B, except that flue liners need not be provided,
(b) have an opening to the outdoors at the top that has an area not less than the cross-sectional area of the shaft which
may be protected from the weather,
(c) terminate not less than 900 mm above the roof surface where it penetrates the roof, and
(d) contain no combustible material, fuel lines or services that are required for use in an emergency.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
(5) Each opening required by Clause (3)(a) must be located so that the top of the opening is not more than 250 mm
below the ceiling, except that the opening may be above the ceiling if the ceiling freely allows passage of air and the
opening into the smoke shaft is provided with a closure that
(a) has a fire-protection rating conforming to Sentence 3.1.8.4.(2) of Division B, except that the temperature on the
unexposed face of the closure is not more than 250°C after 30 min during the fire test and there is no combustible
material within the distances described in Table 4, and except that paint or tightly-adhering paper covering not more
than 1 mm thick shall be exempted from these requirements when applied to a noncombustible backing,
(b) can be opened from a remote location such as a stair shaft, the storey immediately below or the central alarm and
control facility, and
(c) must not open automatically on any floor, other than the fire floor, when smoke or hot gases pass through the shaft.
(6) Closures for openings described in Clause 4(b) are to be openable from the outside and will open automatically on a
signal from a smoke detector in the shaft, by operation of the fire alarm system and when a closure required in
Sentence (5) opens.
(7) A smoke shaft opening referred to in Sentence (2) or (3) that is less than 1 070 mm above the floor must be
protected by guards in conformance with Article 3.3.1.18. of Division B.
(8) In a sprinklered building, the air handling system may be used for smoke venting provided
(a) the system can maintain an exhaust to the outdoors at the rate of six air changes per hour from any floor area, and
(b) emergency power to the fans required by (a) is provided as described in Article 3.2.7.9. of Division B.
(9) Where a closure is required by Sentence (5), the leakage area between closure components and between damper and
frame must be not more than 3 percent of the openable area of the damper.
Page 8 • SB-4
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Table 1
Minimum Size of Vent Openings into Smoke Shafts from Each Floor Area, m 2 (1),(3)
Leakage Area, Building Height, m
Floor Area, m2
%(2) 18 37 73 110 146 183 220 256 293
200 0.1 0.11 0.13 0.15 0.16 0.18 0.19 0.2 0.22
500 0.22 0.25 0.29 0.32 0.36 0.37 0.39 0.41 0.43
1 000 0.43 0.48 0.53 0.59 0.63 0.67 0.71 0.75 0.77
2 000 0.83 0.91 1.01 1.08 1.16 1.22 1.29 1.34 1.39
3 000 1.21 1.33 1.46 1.55 1.67 1.75 1.82 1.9 1.97
4 000 1.62 1.75 1.9 2.02 2.15 2.25 2.35 2.44 2.53
5 000 2.01 2.17 2.34 2.46 2.63 2.74 2.86 2.88 3.07
6 000 2.39 2.57 2.76 2.91 3.1 3.23 3.37 3.47 3.58
200 0.1 0.12 0.15 0.19 0.22 0.27 0.35 0.43 0.55
500 0.23 0.27 0.35 0.4 0.49 0.57 0.69 0.83 1.04
1 000 0.44 0.5 0.71 0.72 0.86 1.01 1.19 1.43 1.73
2 000 0.85 0.97 1.15 1.33 1.56 1.81 2.1 2.48 2.95
3 000 1.26 1.42 1.67 1.91 2.23 2.56 2.97 3.47 4.08
4 000 1.66 1.88 2.18 2.49 2.37 3.28 3.79 4.4 5.16
5 000 2.07 2.32 2.69 3.05 3.51 3.99 4.6 5.32 6.21
6 000 2.47 2.76 3.18 3.59 4.14 4.68 5.37 6.2 7.23
200 0.1 0.13 0.18 0.24 0.37 0.61 1.28 4.6 89.57
500 0.24 0.29 0.39 0.52 0.75 1.13 2.1 6.11 94.5
1 000 0.46 0.55 0.72 0.94 1.3 1.9 3.27 8.29 102.11
2 000 0.88 1.05 1.34 1.73 2.32 3.28 5.36 12.14 116.8
3 000 1.31 1.53 1.95 2.47 3.29 4.58 7.28 15.63 130.83
4 000 1.73 2.01 2.55 3.2 4.23 5.83 9.12 19.97 144.03
5 000 2.15 2.49 3.13 3.92 5.15 7.05 10.9 22.15 157.05
6 000 2.57 2.96 3.73 4.63 6.07 8.26 12.65 25.39 169.29
200 0.11 0.14 0.21 0.37 0.88 2.06
500 0.25 0.31 0.47 0.76 1.58 9
1 000 0.47 0.59 0.86 1.33 2.6 11.99
2 000 0.91 1.12 1.6 2.41 4.47 17.46
3 000 1.35 1.64 2.31 3.43 5.21 22.48
4 000 1.79 2.17 3.02 4.43 7.91 27.29
5 000 2.22 2.68 3.71 5.42 9.55 31.95
6 000 2.65 3.2 4.4 6.39 11.18 36.47
200 0.11 0.15 0.28 0.7 24.83
500 0.25 0.34 0.58 1.33 29.18
1 000 0.49 0.63 1.06 2.27 36.07
2 000 0.95 1.21 1.97 3.99 48.56
3 000 1.41 1.78 2.84 6.63 60.15
4 000 1.86 2.34 3.7 7.22 71.15
5 000 2.21 2.9 4.55 8.79 81.81
6 000 2.75 3.46 5.4 10.33 90.05
Column 1 2 3 4 5 6 7 8 9 10 11
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Table 1 (Cont'd)
Minimum Size of Vent Openings into Smoke Shafts from Each Floor Area, m 2 (1),(3)
Leakage Area, Building Height, m
Floor Area, m2 %(2) 18 37 73 110 146 183 220 256 293
200 0.11 0.16 0.36 3.33
500 0.28 0.36 0.76 5.09
1 000 0.5 0.69 1.37 7.67
2 000 0.99 1.31 2.54 12.35
3 000 1.46 1.94 3.65 16.75
4 000 1.92 2.55 4.75 20.99
5 000 2.4 3.16 5.84 25.11
6 000 2.87 3.74 6.92 29.11
Column 1 2 3 4 5 6 7 8 9 10 11
Notes to Table 1:
(1) The minimum size of a vent opening into a smoke shaft is obtained from Table 1 and is dependent on the floor area and total leakage
area of the smoke shaft walls and closures. This total leakage area may be estimated by adding the leakage areas for the shaft wall
obtained from Table 2 and for the dampered openings obtained from Table 3 provided the cross-sectional area of the smoke shaft, the
opening into the shaft and the opening to the outdoors at the top of the shaft are equal.
(2) Leakage area is the total of the leakage area of smoke shaft wall obtained from Table 2 and the leakage area of openings in smoke
shafts obtained from Table 3.
(3) The size of the vent opening refers to the free or unobstructed area of the opening.
Table 2
Leakage Area of Smoke Shaft Wall
Wall Construction Leakage Area as % of Wall Area
Monolithic concrete 0.5
Masonry wall unplastered 1.5
Masonry wall plastered 0.5
Gypsum board on steel studs 1.0
Column 1 2
Table 3
Leakage Area of Closures into Smoke Shaft
Type of Closure Leakage Area as % of Closure Area(1), (2)
Curtain fire damper 2.5
Single-blade fire damper 3.5
Multi-blade fire damper 4.5
Column 1 2
Notes to Table 3:
(1) Values include allowance for 0.5% leakage between frame and wall construction.
(2) These leakage data contemplate clearances applicable to closures that have been tested in accordance with CAN/ULC-S112-10, "Fire
Test of Fire-Damper Assemblies."
Page 10 • SB-4
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Table 4
Minimum Distance from Closure to Combustible Material
Minimum Distance in Front of Minimum Distance to the Sides
Area of Closure, m2 (1)
or Above Closure, m or Below Closure, m
0.5 0.35 0.20
1.0 0.50 0.25
1.5 0.60 0.30
2.0 0.70 0.35
2.5(2) 0.80 0.40
Column 1 2 3
Notes to Table 4:
(1) For closure areas between those given in Table 4, interpolation may be used to determine the appropriate distances.
(2) For closure areas greater than 2.5 m2, the minimum distance in front of or above the closure shall be one half of the square root of the
closure area, and the minimum distance to the sides or below the closure shall be one quarter of the square root of the closure area.
[3.2.6.7.(1)] Protection of Central Control Room
The design of a room provided for a central alarm and control facility should be adequately protected from fire and smoke
and take into account the nature and sensitivity of the electronic components of the equipment it contains. The room
should also be ventilated with a supply of fresh air in order to maintain a clean environment. Adequate lighting is also
required.
[3.2.6.7.(2)] Central Control Room Air Control
Depending on the method of mechanical venting and air control that is selected for the building, additional controls may be
required at the central alarm and control facility. These additional controls include those with a capability of opening
closures to vents in shafts, stopping air handling systems, and initiating mechanical air supply to stair shafts.
[3.2.6.9.(1)] Testing for Smoke Control
The efficiency of a smoke control system maybe checked by measuring pressure differences and the directions of airflow
around doors and through separating walls of compartments. A pressure meter can be used to measure pressure differences
on either side of a door or partition. Where this is impracticable, a punk stick held near a crack will indicate the direction
of airflow. Measurements of airflow may be taken on the intake side of supply fans or in supply ducts to determine
whether the specified airflow is being provided. In general, airflow should be from the spaces which may be occupied for
various lengths of time during a fire emergency (e.g., vestibules, stair shafts, and elevator hoistways) toward the space in
which the fire is assumed to have occurred. Measurements may be taken at certain critical locations to check the overall
efficiency of the smoke control system.
In buildings where protection is obtained by venting corridors or vestibules to the outdoors, inspection of the building to
determine whether the requirements have been met should be sufficient. Where service shafts are vented to the outdoors at
the top, a check may be made of the wall between the shaft and the uppermost occupied floor areas, to ensure that the
direction of flow is from each floor area into the shaft, when the vent to the outside is open and the outdoor air temperature
is significantly less than that indoors. Where mechanically pressurized vestibules are used, a check may be made to ensure
that the pressure in each vestibule or area of refuge is greater than that in the adjacent floor areas at each floor level.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Doors to stair shafts, elevator hoistways and vestibules in locations subject to pressure differences that may interfere with
normal opening should be checked when the outdoor temperature is near the January design temperature, with the air
injection system operating and a number of windows open to the outdoors on each floor in turn.
Section 2 Scope of Measures for Fire Safety in Existing
High Buildings
This Supplementary Standard includes a number of detailed measures that may be incorporated in a building in order to
comply with the requirements relating to control of smoke for existing buildings. It is not the intention to exclude other
means of attaining the same objectives. Where smoke control methods other than those described in this Supplementary
Standard are developed, they may be based on the information in Appendix B of this Supplementary Standard.
Smoke control measures appropriate to existing buildings vary depending on the height and occupancy of a building. In a
sprinklered building, the requirements for control of smoke movement are minimal (see Measure A, Section 3). In very tall
buildings, limits are placed on the penetration of smoke into exit stairs, elevators for firefighters and all floor areas other
than the one on which fire occurs. Such limits are achieved by Measures B, D, F, H and I in Section 3. In certain buildings
of lesser height and limited population, exit stairs and elevators for firefighters are protected and smoke may be expected to
enter upper floor areas. This situation applies where Measures C, E, G and J, described in Section 3, are employed. In
other buildings, the spread of smoke into shafts and floor areas is accepted, but areas of refuge are provided that are
maintained smoke free, that can be reached by all people in the building within a few minutes and that are linked to
outdoors by safe means of egress. They are described in Measures K and L in Section 3.
Where Measures A, B, D, F, H and I in Section 3 are applied, it is assumed that in the event of fire occupants of the floor
on which the fire occurs will leave by exit stairs immediately following the sounding of a fire alarm, and that occupants of
the floor immediately above the floor on which the fire occurs will be advised to leave by the first fire department officer
on the scene or other person assigned this responsibility. Occupants of all other floors may remain on their floors unless
otherwise directed.
Where Measures C, E, G and J in Section 3 are applied, it is assumed that occupants of all floors will move immediately
into the stair shafts and will then proceed slowly to the outdoors following the sounding of a general fire alarm.
Where Measure K in Section 3 is applied (i.e. the building is divided vertically into two zones), it is assumed that
occupants of the floor on which the fire originates will leave by exit stairs, and that the occupants of all other floors in the
zone in which the fire is discovered will move through vestibules or bridges to floor areas on the same level in the fire-free
smoke control region immediately following the sounding of a fire alarm. Occupants may remain in these areas of refuge
until further directed by the fire department officer.
Where Measure L in Section 3 is applied, it is assumed that occupants of the floor on which the fire originates will leave by
the exit stairs, and that occupants of all other floors will move by corridors or stairs to areas of refuge that are distributed
throughout the building immediately following the sounding of the fire alarm. Occupants may remain in these areas of
refuge until otherwise directed.
In a residential building where reliance is placed on balconies as places of refuge from smoke, as described in Measure M
in Section 3, occupants may remain in their suites when a general fire alarm is given, but should be prepared to move on to
their balconies if conditions in the suite should become untenable.
It is assumed that the cumulative population of storeys below grade divided by 1.8 times the width in metres of all exit
stairs at the storey under consideration will not exceed the 300 limit referred to in Article 3.2.6.1. of Division B, and that
occupants of storeys below grade will evacuate the building by the stair shafts immediately after the discovery of a fire in a
storey below grade.
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2024MMAH Supplementary Standard SB-4
It is also important that firefighters are provided with a smoke-free access to fire floors below grade. Measures A, B, C, D,
E, F, G, L and M include provisions designed to separate the exit stairs serving storeys above grade from those serving
storeys below grade, and to limit entry of smoke into these shafts. Elevator shafts and service shafts are required to be
provided with a separation near grade, or be designed to limit their functioning as paths of smoke movement into upper
floor areas. In Measures H, I and J, no special precautions are necessary to protect shafts in storeys below grade, because
the system of pressurization plus venting of the fire floor protects all shafts, whether or not these penetrate storeys below
grade. In Measure K, the separation into two zones is maintained in storeys below grade. Smoke-free access will thus be
available to any floor on which the fire occurs.
Synopsis of Measures for Fire Safety in High Buildings
Each of the measures is illustrated by a sketch with notes describing the applicable conditions (Figures 1 to 19). These
sketches are intended as a guide to the detailed requirements and as an aid to finding the relative clauses, but they are not
intended to limit in any way the scope of the detailed provisions which in general provide a wider range of choice than can
be shown in the sketches and notes. A summary of requirements applicable to all buildings, regardless of the measure
being used, is given in the following paragraph.
Requirements Common to all Measures for Fire Safety in High Buildings
(1) Elevators controlled by keyed switch (Article 3.2.6.4. of Division B).
(2) Elevator for firefighters required (Article 3.2.6.5. of Division B).
(3) Means of venting each floor area to outdoors by smoke shaft, windows or building exhaust system (Article 3.2.6.6.
of Division B).
(4) Certain floor areas in the building to be sprinklered (Articles 3.2.1.5. and 3.2.2.15. of Division B).
(5) Limits on flame-spread rating and smoke developed classification for interior finish materials in certain locations
(Article 3.1.13.7. of Division B).
(6) Central alarm and control facility required (Article 3.2.6.7. of Division B).
(7) Voice communication system required if building is more than 36 m high (Article 3.2.6.8. of Division B).
(8) Fire protection required for electrical feeders to emergency equipment (Article 3.2.7.10. of Division B).
(9) Power to operate emergency lighting, fire alarm and voice communication systems (Articles 3.2.7.4. and 3.2.7.8. of
Division B).
(10) Emergency power to operate elevators required if building is more than 36 m high (Article 3.2.7.9. of Division B).
2024MMAH Supplementary Standard SB-4
Measure A Fully Sprinklered Building
Figure 1
Typical floor plan, Measure A
Measure A satisfies 3.2.6.2.(1) provision (6) as described in Section 1 for existing sprinklered buildings of any major
occupancy classification.
No limit on height.
All floor areas sprinklered (3.2.6.2.(1) provision (6) as described in Section 1).
Limits on flame-spread ratings and smoke developed classifications described in Sentence 3.1.13.7.(1) of Division B are
relaxed (Sentence 3.1.13.7.(2) of Division B).
1.Door to outdoors in each stair shaft held open during a fire emergency (3A(2))*
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that storey
(3A(3)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3A(3)).
2. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3A(5)).
3. Vertical service spaces, other than elevator shafts, provided with firestops at the first floor below the lowest exit
storey or vented to outdoors at top during a fire emergency (3A(6)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3.2.6.2.(1)
provision (6)(d) as described in Section 1).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
Page 14 • SB-4
2024MMAH Supplementary Standard SB-4
Measure B Open Corridor Access to Stairs and Elevators (including restrictions
on movement of smoke from floor to floor)
Figure 2
Typical floor plan, Measure B
Measure B satisfies 3.2.6.2.(7) provisions (2) to (4) as described in Section 1 for any major occupancy classification. No
limit on height.
1. Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that storey
(3B(3)).*
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3B(3)).
2. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3B(4)).
3. Vertical service spaces, other than elevator shafts, provided with firestops at the first floor below the lowest exit
storey and at intervals of not more than five storeys or vented to outdoors at top during a fire emergency (3B(5)).
4.Open corridor or balcony providing access to stairs and elevator for firefighters (3B(2)).
Elevator shaft and stair shaft heating restrictions.
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3B(6)).
Certain dampers close in air handling ducts during a fire emergency (3B(8)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure C Open Corridor Access to Stairs and Elevators (no additional
restrictions on movement of smoke from floor to floor)
Figure 3
Typical floor plan, Measure C
Measure C satisfies 3.2.6.2.(7) provision (6) as described in Section 1 for Group A, C, D, E or F major occupancy
classification.
Limit on population (3.2.6.2.(7) provision (6) as described in Section 1).
Limited to buildings not more than 75 m high (3.2.6.2.(7) provision (6) as described in Section 1).
1. Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that storey
(3C(3)).*
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3C(3)).
2. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3C(4)).
3.Open corridor or balcony providing access to stairs and elevator for firefighters (3C(2)).
Elevator shaft and stair shaft heating restrictions.
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3C(5)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
Page 16 • SB-4
2024MMAH Supplementary Standard SB-4
Measure D Protected Vestibule Access to Stairs and Elevators (including
restrictions on movement of smoke from floor to floor)
Figure 4
Typical floor plan, Measure D
Measure D satisfies 3.2.6.2.(7) provisions (2) to (4) as described in Section 1 in existing buildings of any major
occupancy classification.
No limit on height.
1.Door to outdoors in each stair shaft held open during a fire emergency (3D(7)). *
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that level
(3D(8)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3D(8)).
2. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3D(13)).
3. Shaft containing an elevator for firefighters is provided with vent to outdoors at bottom during a fire emergency if
the vestibule protection is by pressurization (3D(9)).
4. Vertical service spaces, other than elevator shafts, provided with firestops at the first floor below the lowest exit
storey and at intervals of not more than five storeys or vented to outdoors at top during a fire emergency
(3D(11)).
5.Vestibule vented to outdoors during a fire emergency or pressurized (3D(5)).
Vents to vestibules openable from central control facility if building is more than 36 m high (3D(6)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3D(14)).
Certain dampers close in air handling ducts during a fire emergency (3D(15)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure E Protected Vestibule Access to Stairs and Elevators (no additional
restrictions on movement of smoke from floor to floor)
Figure 5
Typical floor plan, Measure E
Measure E satisfies 3.2.6.2.(7) provision (6) as described in Section 1 for Group A, C, D, E or F major occupancy
classification.
Limit on population (3.2.6.2.(7) provision (6) as described in Section 1).
Limited to buildings not more than 75 m high (3.2.6.2.(7) provision (6) as described in Section 1).
1.Door to outdoors in each stair shaft held open during a fire emergency (3E(6)). *
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that level
(3E(7)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3E(7)).
2. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3E(10)).
No special protection against smoke for elevator shafts or vertical service spaces other than a shaft containing an
elevator for firefighters.
3. Shaft containing an elevator for firefighters is provided with vent to outdoors at bottom during a fire emergency
(3E(8)).
4.Vestibule vented to outdoors during a fire emergency or pressurized (3E(4)).
Vents to vestibules openable from central control facility if building is more than 36 m high (3E(5)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3E(11)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
Page 18 • SB-4
2024MMAH Supplementary Standard SB-4
Measure F Pressurized Stair Shafts and Elevator Shafts (including restrictions on
movement of smoke from floor to floor)
Figure 6
Typical floor plan, Measure F
Measure F satisfies 3.2.6.2.(7) provisions (2) to (4) as described in Section 1 in existing buildings of any major occupancy
classification.
No limit on height.
1.Door to outdoors in each stair shaft held open during a fire emergency (3F(2)). *
Stair shaft pressurized during a fire emergency (3F(2)).
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that level
(3F(3)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3F(3)).
2. Shaft containing an elevator for firefighters is pressurized during a fire emergency (3F(4)).
3. Vertical service spaces, other than elevator shafts, provided with firestops at the first floor below the lowest exit
storey and at intervals of not more than five storeys or vented to outdoors at top during a fire emergency (3F(7)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3F(11)).
Certain dampers in air-handling ducts close during a fire emergency (3F(12)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure G Pressurized Stair Shafts and Elevator Shafts (no additional
restrictions on movement of smoke from floor to floor)
Figure 7
Typical floor plan, Measure G
Measure G satisfies 3.2.6.2.(7) provision (6) as described in section 1 for Group A, C, D, E or F major occupancy
classification.
Limit on population (3.2.6.2.(7) provision (6) as described in section 1).
Limited to buildings not more than 75 m high (3.2.6.2.(7) provision (6) as described in section 1).
1.Door to outdoors in each stair shaft held open during a fire emergency (3G(2)).*
Stair shaft pressurized during a fire emergency (3G(2)).
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that
level (3G(3)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3G(3)).
2. Shaft containing an elevator for firefighters is pressurized during a fire emergency (3G(4)).
3. No special protection against smoke for elevator shafts or vertical service spaces other than a shaft containing an
elevator for firefighters.
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3G(7)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
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2024MMAH Supplementary Standard SB-4
Measure H Building Fully Pressurized
Figure 8
Typical floor plan, Measure H
Measure H satisfies 3.2.6.2.(7) provisions (2) to (4) as described in Section 1 in existing buildings of any major
occupancy classification.
No limit on height
1.All floor areas pressurized during a fire emergency (3H(2)). *
Provision for modulating air supply for building pressurization during warm weather (3H(4)).
2.Fire floor provided with means of venting to outdoors by smoke shaft or windows (3H(7)).
3. A proportion of air for building pressurization directed into stair shafts (3H(2)).
Doors to outdoors in stair shafts not held open during a fire emergency (3H(5)).
4. Except as required for venting, all openings in perimeter walls and roof are kept closed during a fire emergency
(3H(5)).
Except as required for pressurization, air moving fans are stopped during a fire emergency in a system that serves
more than two storeys (3H(4)).
Certain dampers in air handling ducts are closed during a fire emergency (3H(6)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure I Partially Pressurized Building (including restrictions on movement of
smoke from floor to floor outside core)
Figure 9
Typical floor plan, Measure I
Measure I satisfies 3.2.6.2.(7) provisions (2) to (4) as described in Section 1 in existing buildings of any major occupancy
classification.
No limit on height.
1.Enclosing wall of core is a fire separation with self-closing doors.
Central core is pressurized during a fire emergency (3I(2)). *
All openings in perimeter walls and roof of core kept closed during a fire emergency (3I(3)).
2. Fire compartment is vented to outdoors during a fire emergency by smoke shaft or windows (3I(4)).
3. Vertical service spaces, other than elevator shafts, outside core provided with firestops at the level of the first floor
below the lowest exit storey and at intervals of not more than five storeys or vented to outdoors at the top during a
fire emergency (3I(6)).
4. Doors to outdoors in stair shafts not held open during a fire emergency except as required for pressurizing the core
(3I(3)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3I(7)).
Certain dampers in air handling ducts are closed during a fire emergency (3I(8)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
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2024MMAH Supplementary Standard SB-4
Measure J Partially Pressurized Building (no additional restrictions on movement
of smoke from floor to floor outside core)
Figure 10
Typical floor plan, Measure J
Measure J satisfies 3.2.6.2.(7) provision (6) as described in Section 1 for Group A, C, D, E or F major occupancy
classification.
Limit on population (3.2.6.2.(7) provision (6) as described in Section 1).
Limited to buildings not more than 75 m high (3.2.6.2.(7) provision (6) as described in Section 1).
1.Enclosing wall of core is a fire separation with self-closing doors.
Central core is pressurized during a fire emergency (3J(2)). *
All openings in perimeter walls and roof of core are kept closed during a fire emergency (3J(3)).
2.Doors to outdoors in stair shafts not held open during a fire emergency (3J(3)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3J(4))
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure K Vertically Divided Buildings (with spatial separation)
Figure 11
Typical floor plan, Measure K
Measure K satisfies 3.2.6.2.(7) provision (5) as described in Section 1 for buildings of Group A, C, D, E or F major
occupancy classification.
No limit on height.
2.One elevator for fire fighters and one stairshaft in each smoke control region (3K(4)).
3. If bridges do not occur at each storey, two stairshafts are required in each smoke control region (Sentence 3.4.2.1.
of Division B).
4.Building designed as two smoke control regions with spatial separation between (3K(2)).
5. Bridges at intervals of not more than five storeys, except that in buildings of Group C major occupancy more than
75 m high, the bridge is at each storey (3K(3)).
Bridges vented to outdoors or pressurized during a fire emergency (3K(11)).
6. Fire separation in storeys below grade to maintain separation between smoke control regions (3K(15)). Air moving
fans are stopped during a fire emergency in a system that serves more than two storeys (3K(14)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
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2024MMAH Supplementary Standard SB-4
Measure K Vertically Divided Buildings (with fire separation)
Figure 12
Typical floor plan, Measure K
Measure K satisfies 3.2.6.2.(7) provision (5) as described in Section 1 for buildings of Group A, C, D, E or F major
occupancy classification.
No limit on height.
2.One elevator for firefighters and one stair shaft in each smoke control region (3K(4)).
If vestibules do not occur at each storey, two stair shafts are required in each smoke control region (Sentence
3.4.2.1. of Division B).
3.Building designed as two smoke control regions with fire separation between (3K(2)).
Fire separation in storeys below grade to maintain separation between smoke control regions (3K(15)).
4. Vestibule at intervals of not more than five storeys, except that in the case of buildings of Group C major occupancy
more than 75 m high, the vestibule is at each storey (3K(3)).
Vestibules vented to outdoors or pressurized during a fire emergency (3K(11)).
5. Vent to outdoors in each smoke control region on floors below mid height of building (3K(12)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3K(14)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure L Areas of Refuge (duplicate groups of areas of refuge at every fifth
storey except as required in item 5)
Figure 13
Typical floor plan, Measure L
Measure L satisfies 3.2.6.2.(7) provision (5) as described in Section 1 for buildings of Group A, C, D, E or F major
occupancy classification.
No limit on height.
1. Stair shaft and shaft containing an elevator for firefighters protected by area of refuge or vestibule (3L(11)). *
Door to outdoors in each stair shaft held open during a fire emergency (3L(14)).
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that storey
(3L(15)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3L(15)).
2. Stair shaft and shaft containing an elevator for firefighters is protected at intermediate floors by pressurized
vestibules (3L(11)).
3. Shaft containing an elevator for firefighters terminates not lower than the first floor below the lowest exit storey
or has elevator vestibules in every storey below the lowest exit storey (3L(13)).
Shaft containing an elevator for firefighters provided with vent to outdoors at bottom during a fire emergency
(3L(16)).
4. No special protection against smoke for elevator shafts or vertical service spaces other than a shaft containing an
elevator for firefighters.
5. Two areas of refuge on each fifth floor pressurized during a fire emergency (3L(10)), or areas of refuge staggered
on intermediate storeys (see Figure 15), except that in buildings of Group C major occupancy more than 75 m
high the areas of refuge shall be located on each storey.
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3L(18)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
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2024MMAH Supplementary Standard SB-4
Measure L Areas of Refuge (areas of refuge located in pairs)
Figure 14 Figure 15
Typical floor plan, Measure L Typical cross section showing areas of refuge
on intermediate floors
Measure L satisfies 3.2.6.2.(7) provision (5) as described in Section 1 for buildings of Group A, C, D, E or F major
occupancy classification.
No limit on height.
1. Stair shaft and shaft containing an elevator for firefighters protected by area of refuge or vestibule (3L(11)). *
Door to outdoors in each stair shaft held open during a fire emergency (3L(14)).
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that storey
(3L(15)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3L(15)).
2. Two areas of refuge are pressurized during a fire emergency (see Figure 14 for area of refuge every fifth storey),
except that in buildings of Group C major occupancy more than 75 m high, the areas of refuge are located on each
storey (3L(10)).
3. No special protection against smoke for elevator shafts or vertical service spaces other than a shaft containing an
elevator for firefighters.
4. Shaft containing an elevator for firefighters terminates not lower than the first floor below the lowest exit storey or
has elevator vestibules in every storey below the lowest exit storey (3L(13)).
Shaft containing an elevator for firefighters is provided with vent to outdoors at bottom during a fire emergency
(3L(16))
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3L(18)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
2024MMAH Supplementary Standard SB-4
Measure M Building with Balconies
Figure 16
Typical floor plan, Measure M
Measure M satisfies 3.2.6.2.(7) provision (7) as described in Section 1 for existing buildings of Group C major occupancy
classification.
1.Door to outdoors in each stair shaft held open during a fire emergency (3M(2)). *
Stair shaft serving floors below the lowest exit level is separate from stair shaft serving floors above that level
(3M(3)).
Stair shaft serving floors below the lowest exit level is pressurized during a fire emergency (3M(3)).
2.Each suite is provided with a balcony (3.2.6.2.(6) provision (7) as described in Section 1).
3. Elevator shaft terminates not lower than the first floor below the lowest exit storey or has elevator vestibules in
every storey below the lowest exit storey (3M(4)).
Air moving fans are stopped during a fire emergency in a system that serves more than two storeys (3M(5)).
* First number indicates Section number. Letter indicates Measure. Last number indicates number of Sentence in that Measure.
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2024MMAH Supplementary Standard SB-4
Measure N Connected Buildings
Figure 17
Section through buildings linked by underground tunnel
Figure 18
Section through buildings joined at firewall
Figure 19
Section through buildings connected by a bridge
Measure N satisfies Article 3.2.6.3. of Division B for existing connected buildings.
2024MMAH Supplementary Standard SB-4
Section 3 Measures for Life Safety in Existing
High Buildings
Measure A Fully Sprinklered Buildings
General
The steps described in this Measure amount to an adequate smoke control measure, satisfying the requirements for existing
sprinklered buildings. Reliance is placed on the full sprinkler installation to limit fire spread and consequently, the
generation of smoke.
Some additional protection of exit stairs is afforded by the provision of an opening to the outdoors at the foot of the stair
shaft. In cold weather, when stack action is likely to be most significant, this measure may give a general increase in air
pressure in the stair shaft, thus restricting entry of smoke.
In this Measure is included the requirement that elevator shafts and service shafts should not be continuous from above to
below grade, except when vestibules are provided at elevator doors in below grade storeys.
Where Measure A is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is intended
that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk downstairs to the
street floor or to a safe intermediate floor area. Occupants of other floors may remain where they are until advised to
evacuate by the person operating the central alarm and control facility.
Measure A
(1) The requirements for existing sprinklered buildings may be met by incorporating the requirements in Sentences (2)
to (8).
(2) A stairway serving storeys above the lowest exit level has a vent or door to the outdoors at or near the bottom of the
stair shaft, as described in Sentence (4).
(3) A stairway serving floors below the lowest exit level
(a) has a vent or door to the outdoors at or near the top of the stair shaft that has an openable area of not less than
0.1 m2 for each storey served by the stairway, less 0.01 m2 for each weatherstripped door and 0.02 m2 for each non-
weatherstripped door opening into the stair shaft,
(b) is enclosed in a shaft that
(i) does not pass through the floor above the lowest exit level and is separate from a shaft that contains a stairway
serving upper storeys, or is enclosed in a shaft that
(ii) contains a stairway serving upper storeys, but is separated from that stairway at the lowest exit level by a fire
separation having a fire-resistance rating not less than that required for the shaft enclosure, and
(c) is provided with equipment capable of maintaining a flow of air introduced at or near the bottom of the stair shaft, at
a rate equal to 0.47 m3/s for each storey served by the stairway.
(4) A stair shaft required to be vented to the outdoors by Sentence (2) or by other provisions in this Supplementary
Standard is provided with a vent or door that
(a) has an openable area of 0.05 m2 for every door between the stair shaft and a floor area, but not less than 1.8 m2,
(b) opens directly to the outdoors or into a vestibule or exit corridor that has a similar opening to the outdoors, and
(c) has a door or closure that
(i) is openable manually, and
(ii) can remain in this open position during a fire emergency.
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2024MMAH Supplementary Standard SB-4
(5) Any elevator shaft that passes through the floor above the lowest exit storey should not penetrate the floor of the
storey immediately below the lowest exit storey, unless there is a vestibule between the shaft and each floor area below
grade as described in Sentence (3) of Measure D.
(6) A vertical service space, other than an elevator shaft, that passes through the floor above the lowest exit storey,
should be provided with a tight-fitting noncombustible seal or fire stop at the floor level of the storey immediately below
the lowest exit storey, except where the vertical service space is vented to the outdoors at the top as described in Sentence
(10) of Measure F.
(7) A supply of air required by Sentence (3) is carried in ducts as described in Sentence (13) of Measure F.
(8) The central control facility required by Article 3.2.6.7. of Division B is provided with additional controls capable of
(a) opening closures to vents in shafts that may be required by Sentence (6),
(b) stopping air handling systems as required by provisions for existing sprinklered buildings, and
(c) initiating the mechanical air supply to stair shafts as may be required in Sentence (3).
Measures B and C Open Corridor Access to Stairs and Elevators
General
Measures B and C can be applied to a building where habitable floor areas are approached along access ways open to the
outdoors.
Each corridor that provides access to stairs or elevators is permanently open to the outside as shown in Figures 2 and 20.
The situation is illustrated by the pressure characteristic diagram shown in Figure 21. Air flow through openings that may
exist in floors is likely to be more pronounced than with other smoke control methods because of the reduction in the
influence of vertical shafts, so it is desirable that openings through the floor-ceiling assembly be minimized. This should
not, however, present an immediate smoke problem except on the floor directly above the floor where a fire occurs.
Measure C is the same as Measure B, except that no steps are taken to limit smoke movement into upper storeys through
vertical service spaces or shafts in Measure C.
Where shafts enclosing plumbing and electrical services penetrate floor spaces and a decision has been made to use
Measure B for control of smoke movement, these shafts should be sealed at least at every fifth storey at a horizontal fire
separation and at the floor immediately below the lowest exit storey or have vents to the outside at the top. In the latter
case there is still some possibility that smoke may pass into the uppermost floor because the air pressures in these floor
areas are in the same range as the outside pressures. It is therefore important that any leakage areas in the enclosing walls
between floor areas and shaft be kept to a minimum.
In order to avoid creation of pressures that may interfere with the opening of doors to stair shafts and elevator shafts, it is
recommended that the building heating system be so designed that temperatures in heated stair shafts and elevator shafts be
not more than 12°C above outside air temperature.
Where Measure B is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is intended
that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk down stairs to a
safe floor area. In buildings more than 36 m high, occupants of other floors may remain until advised to evacuate by the
person operating the central alarm and control facility.
Where Measure C is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that occupants of all floors will walk down stairs to
the street floor or to a safe intermediate floor area.
2024MMAH Supplementary Standard SB-4
Figure 20 Illustration of Measures B and C designs
Figure 21 Pressure characteristics in a Measure B design
Measure B (including restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit smoke movement in existing buildings may be met by incorporating the
requirements in Sentences (2) to (9).
(2) All public corridors leading to the required exit stairs and elevators for firefighters from every floor area on a floor
above the lowest exit storey are provided with permanent openings to the outdoors that
(a) are distributed along the length of the corridor,
(b) have the top of the opening not more than 250 mm below the ceiling of the corridor, and
(c) have an aggregate open area that is not less than 10 percent of the floor area of the corridor or 1 m2, whichever is
greater.
(3) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(4) Any elevator shaft that passes through the floor above the lowest exit storey should not penetrate the floor of the
storey immediately below the lowest exit storey, unless there is a vestibule between the elevator door or doors and each
floor area below grade as described in Sentence (3) of Measure D.
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2024MMAH Supplementary Standard SB-4
(5) A vertical service space, other than an elevator shaft, within a heated floor area is provided with
(a) tight-fitting noncombustible fire stops located at the level of the floor immediately below the lowest exit storey and
at the level of certain other floors that are fire separations provided the space between fire stops is not more than five
storeys, or
(b) a vent to the outdoors as described in Sentence (10) of Measure F.
(6) Except for exhaust from kitchens, washrooms and bathrooms in dwelling units, air moving fans are stopped during a
fire emergency in an air handling system that serves more than two storeys.
(7) Supply, return and exhaust ducts more than 0.013 m2 in cross-sectional area at the point of entry to a vertical service
space in an air handling system that is required to shut down by the provisions of Sentence (6) are provided with dampers
that will close when the air moving fans are stopped.
(8) Where a supply of air is required by the provisions of Sentence (3), it is carried in ducts as described in Sentence
(13) of Measure F.
(9) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping the air handling systems and closing dampers as required by Sentences (6) and (7),
(b) opening closures to vents in vertical service spaces where required by Sentence (5), and
(c) initiating the air supply to stair shafts as may be required by Sentence (3).
Measure C (no restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit smoke movement in existing buildings may be met by incorporating the
requirements of Sentences (2) to (7).
(2) The public corridors leading to the required exit stairs and elevators for firefighters from every floor area on a floor
above the storey on which egress directly to the outdoors occurs are provided with permanent openings to the outdoors
that
(a) are distributed along the length of the corridor,
(b) have the top of the opening not more than 250 mm below the ceiling of the corridor, and
(c) have an aggregate open area that is not less than 10 percent of the floor area of the corridor or 1 m2, whichever is
greater.
(3) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(4) Any elevator shaft that contains an elevator for firefighters and passes through the floor above the lowest exit storey
should not penetrate the floor of the storey immediately below the lowest exit storey, unless there is a vestibule between
the elevator door or doors and each floor area below grade as described in Sentence (3) of Measure D.
(5) Except for exhaust from kitchens, washrooms and bathrooms in dwelling units, air moving fans are stopped during a
fire emergency in an air handling system that serves more than two storeys.
(6) Where a supply of air is required by Sentence (3), it is carried in ducts described in Sentence (13) of Measure F.
(7) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping the air handling systems as required by Sentence (5), and
(b) initiating the air supply to stair shafts as may be required by Sentence (3).
2024MMAH Supplementary Standard SB-4
Measures D and E Protected Vestibule Access to Stair shafts and
Elevator Shafts
General
In Measures D and E, movement of smoke through stair shafts and elevator shafts is limited by the provision of vestibules
that are either open to the outdoors during a fire emergency or have outdoor air injected into them. Stair shafts are further
protected by opening a door to the outdoors at the bottom of the shaft. Where vestibules are protected by the injection of
outdoor air, the elevator shaft is provided with a large opening to the outdoors at the bottom.
Where provisions to limit the movement of smoke in existing buildings requires the movement of smoke into floor areas to
be limited, service shafts are either sealed at intervals or provided with an opening to the outdoors at the top of the shaft as
described in Measure B. A typical plan of a building in which this method of smoke control is appropriate is shown in
Figure 4.
Measure E is the same as Measure D, except that no measures are taken to limit movement of smoke into upper storeys in
Measure E.
Where a vestibule has a vent or opening to the outdoors that is much larger than the leakage area around doors between the
vestibule and other parts of the building, the air pressure in the vestibule will be approximately equal to the outdoor
pressure at the same level. This is illustrated in Figure 7. In cold weather in storeys below the neutral pressure plane, air
pressure in the vestibule will be substantially higher than that in the floor area. Air will tend to flow from the vestibule into
the floor area. In upper storeys the air pressure in the vestibules will be less than that in the floor area, and air will flow
from the floor area to the vestibule. The vent or opening at the foot of the stair shaft referred to above has the effect of
increasing pressure in the shaft, so that it approaches outdoor air pressure at ground level (see Figure 22). On upper storeys
the pressure in the stair shaft will be higher than that in the vestibules, and smoke that may enter the vestibules will not pass
into the stair shaft.
In warm weather when outdoor air may be as warm or warmer than that inside a building, the stack effect is likely to be
minimal. In these circumstances, the major problem is expansion of the hot gases on the fire floor. This will tend to force
air around doors into the vestibule. The large vent opening, however, will create a situation where the greater proportion of
the air entering the vestibule will pass to the outdoors and a much smaller quantity may enter the shafts. The effect of wind
is variable and difficult to predict. In warm weather the effect may be to protect vestibules on one side of the building and
to allow smoke to enter those on the other side.
Figure 22
Pressure characteristics in a Measure D building with vented shafts
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2024MMAH Supplementary Standard SB-4
Where air is injected into vestibules, the pressure characteristics in cold weather are likely to be as shown in Figure 23.
The rates of air injection should be sufficient to keep the pressures in the vestibules a little higher than the pressure in the
shaft. This limits the possibility of movement of smoke into the vestibules from the floor areas. In cold weather vents at
the bottom of the stair shafts and elevator shafts provide additional protection.
Service shafts that will not be used in a fire emergency are provided with vents at the top to the outdoors where Measure D
(but not Measure E) requires that movement of smoke into upper floors be limited. However, some smoke may pass from
top vented service shafts into the top floor or floors, because air pressures at the top of the shafts and in the floor area of the
top storey are approximately equal.
Stack action and the operation of smoke control measures may provide pressures that will interfere with the normal
operation of certain doors. Where a vestibule is vented to the outdoors, this may apply to any door between a vestibule and
an elevator shaft that is farther above or below the mid-height of a building than the height given by Graph 8 in
Appendix A of this Supplementary Standard and to any door between a vestibule and a stair shaft that is farther above
grade than the height given by Graph 8. Where a vestibule is pressurized, this may apply to any door between a vestibule
and a floor space that is farther above grade than the height shown in Graph 8.
Figure 23
Pressure characteristics in a Measure D building having air injected into vestibules
As an alternative to the provision of a mechanical air supply for a vestibule to an elevator shaft, as described in Sentence
(5) of Measure D, the mechanical air supply can be introduced directly into the shaft as described in Sentence (4) of
Measure F provided there are no open vents to the elevator shaft as described in Sentence (9) of Measure D.
Where a mechanical air supply is required by Sentence (5) of Measure D and Sentence (4) of Measure E, it may be
desirable to heat the air supply and to provide two air intakes in separate locations on the building face as discussed in the
general provisions to Measures F and G.
Where Measure D is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk down
stairs to the street floor or to a safe intermediate floor area. Occupants of other floors may remain until advised to evacuate
by the person operating the central alarm and control facility.
Where Measure E is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that occupants of all floors will walk down stairs to
the street floor or to a safe intermediate floor area.
2024MMAH Supplementary Standard SB-4
Measure D (including restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements of Sentences (2) to (17).
(2) Between each floor area and each stair shaft or elevator shaft that contains an elevator for firefighters, a vestibule is
provided as described in Sentence (3).
(3) Where a vestibule is required by Sentence (2) or by other provisions of this document
(a) a fire separation is provided between a public corridor and the vestibule that has a fire-resistance rating of not less
than 45 min,
(b) a fire separation is provided between a floor area, other than the corridor described in Clause (a), and the vestibule
that has a fire-resistance rating not less than that required for an exit in Article 3.4.4.1. of Division B,
(c) a fire separation is provided between a stair or elevator enclosure and the vestibule that has a fire-resistance rating
not less than that required for an exit in Article 3.4.4.1. of Division B, and
(d) a door in the fire separation described in Clauses (a), (b) or (c) (except for an elevator door) is provided with a
self-closing device as required by Article 3.1.8.13. of Division B, and opens in the direction of travel from the floor
area to the exit stairway.
(4) On each floor any vestibule that has a door to an exit stair may also have a door to an elevator for firefighters, but
two exit stairs may not open onto the same vestibule.
(5) Each vestibule described in Sentence (2) that provides access to a stair shaft or an elevator shaft
(a) has a vent opening to the outdoors that has an opening area not less than 0.1 m2 for each door that opens onto the
vestibule, but not less than 0.4 m2, or
(b) has equipment capable of providing for a vestibule to a stair shaft or an elevator shaft a mechanical air supply not
less than that obtained from Graph 3 in Appendix A of this Supplementary Standard.
(6) The vent to each vestibule referred to in Clause (5)(a) may be provided with a closure that is openable manually, and
in a building that is more than 36 m high, it can be opened from the central control facility as provided in Sentence (17).
(7) A stairway serving storeys above the lowest exit level is vented to the outdoors at the bottom of the stair shaft as
described in Sentence (4) of Measure A.
(8) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(9) Each elevator shaft protected by a vestibule having a mechanical air supply as described in Clause (5)(b) has a vent
at or near the bottom of the shaft, opening directly to the outdoors or into a vestibule or corridor that has a similar opening
to the outdoors, having an openable area not less than 0.02 m2 for every door into the shaft, other than doors at street floor
level.
(10) The vent at the bottom of an elevator shaft referred to in Sentence (9) may be provided with a closure which is
openable manually and is designed to remain open during a fire emergency.
(11) A vertical service space other than an elevator shaft is provided with
(a) a tight-fitting noncombustible fire stop at the level of the floor immediately below the lowest exit storey, and at the
level of certain other floors that are fire separations, provided the space between fire stops is not more than five
storeys, or
(b) a vent to the outdoors as described in Sentence (10) of Measure F.
(12) Except as provided in Sentence (13), an elevator shaft other than a shaft that contains an elevator for firefighters is
protected against entry of smoke by a vestibule as described in Sentence (5).
(13) The provisions in Sentence (12) are waived for an elevator shaft that serves floor areas below the lowest exit storey
and does not penetrate the floor immediately above that storey.
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2024MMAH Supplementary Standard SB-4
(14) Except for air moving fans supplying vestibules as provided in Clause (5)(b), and except for exhaust from kitchens,
washrooms and bathrooms in dwelling units, air moving fans are stopped during a fire emergency in an air handling
system that serves more than two storeys.
(15) In an air handling system that is required to shut down by the provisions of Sentence (14), supply, return and
exhaust ducts more than 130 cm2 in cross-sectional area at the point of entry to a vertical service space are provided at
that point with dampers that will close when air moving fans are stopped.
(16) Where a supply of air is required by the provisions of Sentences (5) and (8), it is carried in ducts described in
Sentence (13) of Measure F.
(17) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) opening closures to vents to the outdoors in vestibules on all floors as required by Sentence (6), and in elevator
shafts as required by Sentence (9),
(b) stopping air handling systems and closing dampers in ducts as required by Sentences (14) and (15),
(c) initiating the mechanical air supply to vestibules required by Clause (5)(b), and
(d) opening closures to vents in vertical service spaces where required by Sentence (11).
Measure E (no restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (13).
(2) Between each floor area and each stair shaft or each elevator shaft that contains an elevator for firefighters, a
vestibule is provided as described in Sentence (3) of Measure D.
(3) On each floor any vestibule that has a door to an exit stair shaft may also have a door to an elevator for firefighters,
but two exit stairs may not open onto the same vestibule.
(4) Each vestibule described in Sentence (2) that provides access to a stair shaft or an elevator shaft
(a) has a vent opening to the outdoors that has an openable area of not less than 0.1 m2 for each door that opens onto the
vestibule but not less than 0.4 m2, or
(b) has equipment capable of providing for a vestibule to a stair shaft or an elevator shaft a mechanical air supply not
less than that obtained from Graph 3 in Appendix A of this Supplementary Standard.
(5) The vent to each vestibule referred to in Clause (4)(a) is provided with a closure that is openable manually, and in a
building that is more than 36 m high can be opened from the central control facility as provided in Sentence (13).
(6) A stairway serving storeys above the lowest exit level is vented to the outdoors at the bottom of the stair shaft as
described in Sentence (4) of Measure A.
(7) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(8) Each elevator shaft protected by a vestibule having a mechanical air supply as described in Clause (4)(b) has a vent
at or near the bottom of the shaft opening directly to the outdoors, or into a vestibule or corridor that has a similar opening
to the outdoors, having an openable area not less than 0.02 m2 for every door into the shaft other than doors at street floor
level.
(9) The vent at the bottom of an elevator shaft referred to in Sentence (8) may be provided with a closure that is
openable manually and is designed to remain open during a fire emergency.
(10) Any elevator shaft that contains an elevator for firefighters and passes through the floor above the lowest exit storey
does not penetrate the floor of the storey immediately below the lowest exit storey except where there is a vestibule
between the elevator door or doors and each floor area below grade as described in Sentence (3) of Measure D.
2024MMAH Supplementary Standard SB-4
(11) Except for air moving fans supplying vestibules as provided in Clause (4)(b), and except for exhaust from kitchens,
washrooms and bathrooms in dwelling units, air moving fans are stopped during a fire emergency in an air handling
system that serves more than two storeys.
(12) Where a supply of air is required by the provisions of Sentences (4) and (7), it is carried in ducts described in
Sentence (13) of Measure F.
(13) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) opening closures to vents to the outdoors in vestibules on all floors as required in Sentence (5),
(b) stopping air handling systems as required by Sentence (11), and
(c) initiating the mechanical air supply to vestibules as required by Clause (4)(b).
Measures F and G Pressurized Stair Shafts and Elevator Shafts
General
Measures F and G are suitable for use in buildings that have central cores containing elevator shafts and stair shafts and in
buildings that have a spine corridor. The objective is to inject sufficient air from outdoors to provide air pressures in stair
shafts and in one or more protected elevator shafts that will be at least equal to the outdoor air pressure at ground level.
Protected elevator shafts may, in addition, be provided with vestibules on each floor in order to reduce the effect of the
large leakage areas around elevator doors, which may otherwise require injection of excessive quantities of air in order to
achieve the desired pressurization. An opening to the outdoors at the bottom of each stair shaft is required in conjunction
with air injection in order to maintain the desired pressure conditions, though some doors on upper floors may be held open
for a time, and to provide for dilution of smoke that may enter the stair shaft. A typical plan of a building where this
method of smoke control is appropriate is shown in Figure 6.
Measure G is the same as Measure F, except that no provisions are made in Measure G to limit movement of smoke into
upper floors by way of service shafts and unprotected elevator shafts.
Where smoke control measures in existing buildings requires that movement of smoke into floor areas be limited, service
shafts, other than elevator shafts, are either sealed at intervals or vented to the outdoors at the top, as described in the
general provisions of Measures B and C. This system is, however, likely to be more efficient than that achieved by
Measure D, because injection of air into some shafts has the effect of increasing the air pressure in all floor areas. This is
illustrated in Figure 24, where the pressure in the floor area of the top storey is greater than that at the top of the vented
shaft.
Figure 24
Pressure characteristics in a Measure F building
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2024MMAH Supplementary Standard SB-4
Treads and landings in a stair shaft present an obstacle to free flow of air. Where air is injected only at the top of a stair
shaft, there is likely to be a pressure gradient between the top and the bottom of the stair shaft. This may produce pressure
differences of sufficient magnitude to interfere with the opening of doors into the stair shaft in the upper part of the
building. This is discussed more fully in Appendix B of this Supplementary Standard.
Stack action and the operation of smoke control measures may produce pressures across certain doors that will interfere
with their normal operation. These pressures may affect any door between a floor space and a stair shaft or an elevator
vestibule that is farther above grade than the height shown in Graph 8 in Appendix A of this Supplementary Standard.
In order to avoid excessive pressures across doors when outdoor temperatures are appreciably above the January design
temperatures, it is recommended that the air flow into elevator shafts in buildings employing Measures F or G be reduced,
but not to less than that obtained by the factor F4 = 5.59 according to the proportion of the air flow referred to in Sentence
(4) of Measure F and Sentence (4) of Measure G. The flow reduction factors are shown in Graph 6 in Appendix A of this
Supplementary Standard.
The limits are such that no modulation is required for a building whose maximum height is not more than the value in
Column 2 of Table 5, provided the January design temperature is not less than the corresponding value in Column 1.
Table 5
Maximum Height of Building Not Requiring Airflow Modulation
Minimum January Design Temperature, °C Maximum Height of Building, m
-7 94
-18 70
-29 55
-40 46
Column 1 2
Heating of the air supply referred to in Sentences (2) and (4) of Measure F or Sentences (2) and (4) of Measure G may be
necessary, since to maintain the efficiency of the smoke control measures the temperature of the incoming air should be not
less than the mean of indoor and outdoor temperatures at the time. To avoid damage to water systems, the temperature of
air entering critical locations should be not less than 0°C. To maintain tolerable conditions for occupants, the temperature
of air entering occupied spaces should be not less than 10°C.
Where a mechanical air supply is specified in Sentences (2) and (4) of Measure F or Sentences (2) and (4) of Measure G,
the air should be drawn from at least two remote locations, each on a different face of the building. Each air intake should
be provided with a damper that will close on a signal from a smoke detector in the duct following 30 s exposure to smoke
or other products of combustion. The damper should have a manual override to reopen it when the smoke condition that
caused it to close has cleared.
Where Measure F is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk down
stairs to the street floor or to a safe intermediate floor area. Occupants of other floors may remain until advised to evacuate
by the person operating the central alarm and control facility.
Where Measure G is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that occupants of all floors will walk down stairs to
the street floor.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Measure F (including restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (14).
(2) A stair shaft serving storeys above the lowest exit level has
(a) a vent or door to the outdoors at or near the lowest exit level of the stair shaft, as described in Sentence (4) of
Measure A, except that the vent or door will open when the air supply referred to in Clause (b) is initiated, and
(b) equipment capable of providing to the shaft a mechanical air supply of not less than 4.72 m3/s plus 0.094 m3/s for
every door opening into the stair shaft.
(3) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(4) An elevator shaft that contains an elevator for firefighters is provided with equipment capable of maintaining a flow
of air to the shaft that is not less than that obtained from Graph 4 in Appendix A of this Supplementary Standard.
(5) Where an elevator shaft referred to in Sentence (4) is provided with a vestibule on every floor, the vestibule
enclosure conforms to Sentence (3) of Measure D.
(6) Any elevator shaft that contains an elevator for firefighters and passes through the floor above the lowest exit storey
should not penetrate the floor of the storey immediately below the lowest exit storey, except where each floor area below
the lowest exit storey is provided with a vent to the outdoors that
(a) has a net area of not less than 0.2 m2 for every 1 000 m2 of floor area,
(b) will remain open during a fire emergency, and
(c) may be incorporated in the conventional exhaust duct system serving storeys below grade.
(7) A vertical service space, other than an elevator shaft, is provided with
(a) a tight-fitting fire stop at the level of the floor immediately below the lowest exit storey and at the level of certain
other floors that are fire separations provided the space between fire stops is not more than five storeys, or
(b) a vent to the outdoors as described in Sentence (10).
(8) Except as provided in Sentence (9), an elevator shaft, other than a shaft that contains an elevator for firefighters, is
pressurized as described in Sentence (4).
(9) The provisions of Sentence (8) are waived for an elevator shaft that serves floor areas below the lowest exit storey
and does not penetrate the floor immediately above that storey.
(10) Where a vent to the outdoors is required by Sentence (7) or other provisions of this document, the vent
(a) if it is a vertical service space in a building in which other shafts are not mechanically pressurized, has an openable
area that is not less than that obtained from Graph 1 in Appendix A of this Supplementary Standard, or if it is in a
building in which other shafts are mechanically pressurized, has an openable area that is not less than that obtained
from Graph 2 in Appendix A of this Supplementary Standard,
(b) if it is in a shaft serving floor areas above the lowest exit storey, is located at or near the top of the shaft where the
top of the shaft is above the mid-height of the building, or at or near the foot of the shaft at or near the exit level
where the top of the shaft is below the mid-height of the building,
(c) if it is in a shaft serving floor areas below the lowest exit storey, is located at or near the top of the shaft, and
(d) if it is provided with a closure, is openable both manually and on a signal from a smoke detector located at or near
the top of the shaft and by a control device located at the central alarm and control facility referred to in Article
3.2.6.7. of Division B.
(11) Except for air moving fans supplying stairs and elevators as provided in Sentences (2) to (4) and, except for exhaust
from kitchens, washrooms and bathrooms in dwelling units, air moving fans in an air handling system that serves more
than two storeys are capable of being stopped as provided in Sentence (14).
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2024MMAH Supplementary Standard SB-4
(12) In an air handling system that is required to shut down by the provisions of Sentence (11), supply, return and
exhaust ducts more than 130 cm2 in cross-sectional area at the point of entry into a vertical service space are provided
with dampers that will close when air moving fans are stopped.
(13) Where a supply of air is required by the provisions of Sentences (2), (3) or (4) or by other provisions of this
document, the duct system is installed in a service space conforming to Section 3.6. of Division B or is otherwise
protected against the effect of fire from the point of fresh air intake to the shaft or to the storey that contains the protected
floor area, vestibule or area of refuge that is required to be so protected.
(14) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping air handling systems and closing dampers in ducts required in Sentences (11) to (13),
(b) initiating the mechanical air supply to stair shafts and elevator shafts required in Sentences (2) to (4), and
(c) opening closures to vents in vertical spaces where required in Sentence (7).
Measure G (no restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (9).
(2) A stair shaft serving storeys above the lowest exit level has
(a) a vent or door to the outdoors at or near the lowest exit level of the stair shaft described in Sentence (4) of
Measure A, except that the vent or door will open when the air supply referred to in Clause (b) is initiated, and
(b) equipment capable of providing to the stair shaft a mechanical air supply of not less than 4.72 m3/s, plus 0.094 m3/s
for every door opening into the stair shaft.
(3) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(4) An elevator shaft that contains an elevator for firefighters is provided with equipment capable of maintaining a flow
of air to the shaft that is not less than that obtained from Graph 4 in Appendix A of this Supplementary Standard.
(5) Where an elevator shaft referred to in Sentence (4) is provided with a vestibule on every floor, the vestibule
enclosure is as described in Sentence (3) of Measure D.
(6) Any elevator shaft that contains an elevator for firefighters and passes through the floor above the lowest exit storey
should not penetrate the floor of the storey immediately below the lowest exit storey, except where each floor area below
the lowest exit storey is provided with a vent to the outdoors that
(a) has a net area of at least 0.2 m2 for every 1 000 m2 of floor area,
(b) will remain open during a fire emergency, and
(c) may be incorporated in the conventional exhaust duct system serving storeys below grade.
(7) Except for air moving fans supplying stair shafts and elevator shafts as provided in Sentences (2) to (4) and, except
for exhaust from kitchens, washrooms and bathrooms in dwelling units, air moving fans in an air handling system that
serves more than two storeys are capable of being stopped as provided in Sentence (9).
(8) Where a supply of air is required by Sentences (2) to (4), it is carried in ducts as described in Sentence (13) of
Measure F.
(9) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping air handling systems as required by Sentence (7), and
(b) initiating the mechanical air supply to stair shafts and elevator shafts as required by Sentences (2) to (4).
2024MMAH Supplementary Standard SB-4
Measure H Fully Pressurized Buildings
General
Measure H is appropriate for buildings having central cores that contain stair shafts and elevator shafts and windows that
are not normally opened, as shown in Figure 8. The air pressure in the whole building is increased so that at grade level it
is at least equal to outdoor air pressure. When a vent to the outdoors is provided on the fire floor by a window in an
exterior wall, by an opening into a smoke shaft as described in Section 1 or by the building mechanical exhaust system if
the building is sprinklered, the pressure in the floor area is reduced substantially, as is shown in Figure 25. Air will then
flow from the shafts and other floor areas into the fire floor. The combination of building pressurization and venting of the
fire floor provides that smoke will not pass into other floor areas or shafts other than the smoke shaft.
Figure 25
Pressure characteristics in a Measure H building
It is important that air be uniformly distributed throughout the building. This may be achieved by supplying the air through
the conventional duct system or through vertical shafts. A minimum proportion of the air is required to be injected directly
into stair shafts. This is designed to reduce the possibility, particularly in warm weather, that a substantial drop in pressure
will occur in these shafts when a door to the outdoors at grade is opened, with the consequent danger that smoke will enter
the shafts.
Where venting is by smoke shafts, the air supply to the floor on which fire occurs should be cut off by closing the dampers
on that floor in order not to overload the smoke shaft.
The total air flow for building pressurization is modulated relative to outdoor air temperature. This is intended, in part, to
limit the potential pressure drop in stair shafts and elevator shafts referred to above and, in part, to avoid excessive
pressures across doors to stair shafts and elevator shafts that would interfere with their normal use.
This requirement for modulation of air flows applies generally to higher buildings. The conditions described in Sentence
(3) of Measure H are such that no modulation is required where the January design temperature and the building height are
as shown in Table 1.
In Toronto, for example, where the January design temperature is -18°C, no modulation of air flow would be required for a
building not more than 70 m high.
This measure is not appropriate for a building where windows may normally be held open. The air flow requirements in
Graph 5 in Appendix A of this Supplementary Standard are based on an assumed air leakage through the external walls that
is appropriate to modern air-conditioned buildings having reasonably tight-fitting non-openable windows. If the leakage
area is other than that noted above, the air flow requirement must be adjusted proportionately, as described in the notes to
Graph 5.
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This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Stack action and the operation of smoke control measures may produce pressures across certain doors that will interfere
with their normal operation. This may apply to any door between a floor space and stair shaft or an elevator shaft that is
farther above grade than the height shown in Graph 8 in Appendix A of this Supplementary Standard.
Where a mechanical air supply is required by Sentence (2) of Measure H, it may be desirable to heat the air supply and to
provide two air intakes in separate locations on the building face, as discussed in the general provisions to Measures F and
G.
Where a floor area is subdivided by walls, provision should be made for a free air passage from any part of the floor area to
the vent or vents required by Sentence (6) of Measure H. Such provisions for venting need not apply to public corridors or
washrooms that normally have a minimum of combustibles.
There should be no problem where vents are on outside walls, and each room or space can be vented directly to the
outdoors. Where a smoke shaft is used, however, a fire may occur in a space adjacent to a stair shaft or elevator shaft
which is separated by partitions from the smoke shaft vent. The solution may be to vent each space to the smoke shaft
through the ceiling plenum or to provide suitable openings in the partitions. Where each room or space opens on to a
corridor leading to stair shafts and elevator shafts, location of the smoke shaft vent in the corridor will be effective in
limiting movement of smoke to other floors, but may also present problems to the firefighter, who may have to approach
the fire through a smoke-filled corridor.
Where Measure H is adopted, and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk down
stairs to the street floor or to a safe intermediate floor area. Occupants of other floors may remain until advised to evacuate
by the person operating the central alarm and control facility.
Measure H
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (9).
(2) The building air handling system is designed and installed so that
(a) supply fans are capable of maintaining an air flow into the building not less than that obtained from Graph 5 in
Appendix A of this Supplementary Standard when the outdoor air temperature is equal to the January design
temperature on a 2.5 percent basis, and
(b) a portion of the air flow referred to in Clause (a) is directed into each stair shaft in a quantity equal to 0.094 m3/s for
every weatherstripped door into the stair shaft and 0.142 m3/s for every non-weatherstripped door into the stair shaft.
(3) Exit stairs shall discharge to the outdoors through a vestibule described in Sentence (3) of Measure D and be
provided with a mechanical air supply of not less than 0.094 m3/s per weatherstripped door and 0.189 m3/s per non-
weatherstripped door in the vestibule, except that the vestibule may be a corridor, lobby or other space.
(4) When smoke control measures are initiated by the controls referred to in Sentence (9)
(a) all main return and exhaust fans are stopped,
(b) supply fans provide the air flow into the stair shafts described in Clause (2)(b), and
(c) supply fans maintain an air flow into the building controlled in relation to outdoor air temperature, so that the total
air flow into the building is substantially equal to the proportion of the air flow referred to in Clause (2)(a) shown in
Graph 6 in Appendix A of this Supplementary Standard, but not less than the air flow obtained when the factor F6
equals 0.0025.
(5) All openings in external walls and roofs, including vents to vertical service spaces other than those referred to in
Sentence (7), have closures that will close as provided in Sentence (9).
(6) All return and exhaust ducts more than 130 cm2 in cross-sectional area at the point of entry to a vertical service
space are provided with dampers that will close on the floor on which fire occurs as required by Sentence (9), other than
those covered by Sentence (7).
2024MMAH Supplementary Standard SB-4
(7) In order to achieve a reduction in air pressure on the floor on which fire occurs relative to that on other floors, means
of venting each floor space to the outdoors are provided as described in Section 1.
(8) Where a supply of air is required by Sentence (2), it is carried in ducts as described in Sentence (13) of Measure F.
(9) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
capable of
(a) stopping main return and exhaust fans and maintaining the air flow in the supply systems as provided in
Sentence (2),
(b) closing the closures and dampers required in Sentences (5) and (6), and
(c) opening closures to the vent openings on the fire floor as provided in Sentence (7).
Measures I and J Partially Pressurized Buildings
General
Measures I and J are very similar to Measure H, except that they may be applied to buildings where windows may be open
during normal use. They are thus particularly suitable for controlling smoke movement in residential buildings. Plans of
typical buildings where Measures I and J are appropriate are shown in Figures 9 and 10. The central core, which includes
exit stair shafts, elevator shafts and public corridors, is separated from the remainder of the floor areas. It is important that
the leakage area of walls around the core be less than that of the exterior walls of the building.
Measure J is the same as Measure I, except that no provision is made in Measure J to limit smoke movement into upper
floors by way of vertical shafts and ducts that are outside the core.
Air is injected into the core so that the air pressure in the core at the ground floor is equal to exterior air pressure at the
same level. Provision of a vent to the outdoors in the fire suite will cause air to flow from adjacent parts of the building
into the fire suite. This is the only method, apart from Measure B, that enables smoke to be confined to the fire suite.
Where movement of smoke from floor to floor outside the central core is to be limited as in Measure I (but not J), all
vertical service shafts, other than elevator shafts, penetrating floor areas must be sealed at intervals or vented to the
outdoors at the top, as discussed in the general requirements of Measure D.
The air flow requirements in Graph 5 in Appendix A of this Supplementary Standard are based on the air leakage
characteristics of typical corridor walls and doors. If the leakage areas exceed those given in the notes to Graph 5, the air
flow should be increased in direct proportion.
Stack action and the operation of smoke control measures may produce pressures across certain doors that will interfere
with their normal operation. This may apply to any door between a suite and a corridor that swings into the corridor and is
farther above grade than the height shown in Graph 8 in Appendix A of this Supplementary Standard.
Within a suite that is subdivided by partitions, the space that includes the vent to the outdoors described in Sentence (4) of
Measure I should be in the same space as the door to the public corridor or linked to it by a leakage area of not less than
0.05 m2.
Where a mechanical air supply is required by Sentence (2) of Measure I and Sentence (2) of Measure J, it may be desirable
to heat the air supply and to provide two air intakes in separate locations on the building face as discussed in the general
provisions to Measures F and G.
Where Measure I is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is intended
that a fire alarm will sound on all floors simultaneously, and that the occupants of the fire floor will walk down stairs to the
street floor or to a safe intermediate floor area. Occupants of other floors may remain until advised to evacuate by the
person operating the central alarm and control facility.
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2024MMAH Supplementary Standard SB-4
Where Measure J is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is intended
that a fire alarm will sound on all floors simultaneously, and that occupants of all floors will walk down stairs to the street
floor or to a safe intermediate floor area.
Measure I (including restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (10).
(2) The building air handling system is designed and installed so that supply fans are capable of maintaining an air flow
into the space that includes all required exit stair shafts, all shafts containing elevators for firefighters and public
corridors, not less than that obtained from Graph 5 in Appendix A of this Supplementary Standard, when the outdoor air
temperature is equal to the January design temperature on a 2.5 percent basis.
(3) Any vent at the top of a vertical service shaft within the central core and all other openings penetrating the space that
includes the stair shafts, elevator shafts and public corridors are provided at the point of penetration with closures that will
close in the event of a fire, as provided in Sentence (10).
(4) Means of venting each fire compartment to the outdoors are provided by
(a) an opening in an exterior wall, such as an openable window or panel, having an openable area of not less than
0.4 m2,
(b) an opening into a smoke shaft, as described in Section 1, operated by a smoke detector, or
(c) an exhaust system, such as a kitchen or washroom exhaust, that has an air flow to the outdoors of not less than
0.189 m3/s per fire compartment served, provided the exhaust system is designed to function as a smoke shaft and
meets the relevant requirements of Section 1.
(5) Where a closure is provided in an opening referred to in Clauses (4)(a) or (b) it will open
(a) by operation of a fusible link, or
(b) on a signal from a smoke detector in the room or suite.
(6) A vertical service space that is outside the pressurized space referred to in Sentence (2) is provided with
(a) a tight-fitting noncombustible seal or fire stop
(i) at the level of the floor immediately below the storey in which egress directly to the outdoors occurs, and
(ii) at the level of certain other floors that are fire separations, provided the space between fire stops is not more
than five storeys, or
(b) a vent to the outdoors as described in Sentence (10) of Measure F.
(7) Except as otherwise provided in Sentences (2) and (4), and except for exhaust from kitchens, washrooms and
bathrooms in dwelling units, air moving fans are stopped during a fire emergency in an air handling system that serves
more than two storeys.
(8) In an air handling system that is required to shut down by Sentence (7), supply, return and exhaust ducts more than
0.013 m2 in cross-sectional area at the point of entry to a vertical service space are provided with dampers that close when
the air moving fans are stopped.
(9) Where a supply of air is required by Sentence (4), it is carried in ducts as described in Sentence (13) of Measure F.
(10) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping return and exhaust fans, closing dampers in ducts and maintaining the air flow in the supply system to the
space that includes stair shafts, elevator shafts and corridors as provided in Sentences (2) and (7),
(b) causing dampers and closures in the enclosing walls of the space that includes stair shafts, elevator shafts and
corridors to close as required by Sentence (3),
(c) opening closures to vents in vertical service spaces where required by Sentence (6),
(d) opening closures in vents referred to in Sentence (4), individually or in groups limited to one floor at a time, and
(e) initiating the air flow in the exhaust system from any floor, where required by Clause (4)(c).
2024MMAH Supplementary Standard SB-4
Measure J (no restriction on the movement of smoke from floor to floor)
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements in Sentences (2) to (6).
(2) The building air handling system is designed and installed so that supply fans are capable of maintaining an air flow
into the space that includes all required exit stair shafts, all shafts containing elevators for firefighters and public
corridors, not less than that obtained from Graph 5 in Appendix A of this Supplementary Standard, when the outdoor air
temperature is equal to the January design temperature on a 2.5 percent basis.
(3) Any vent at the top of a vertical service shaft within the central core, and all other openings penetrating the space
that includes the stair shafts, elevator shafts and public corridors, are provided at the point of penetration with closures
that will close in the event of fire, as provided in Sentence (4).
(4) Except as otherwise provided in Sentence (2), and except for exhaust fans from kitchens, washrooms and bathrooms
in dwelling units, air moving fans are stopped during a fire emergency in an air handling system that serves more than
two storeys.
(5) Where a supply of air is required by Sentence (2), it is carried in ducts as described in Sentence (13) in Measure F.
(6) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping return and exhaust fans and maintaining the air flow in the supply system to the space that includes stair
shafts, elevator shafts and corridors as provided in Sentence (2), and
(b) causing dampers and closures in the enclosing walls of the space that includes stair shafts, elevator shafts and
corridors to close as required by Sentence (3).
Measure K Vertically Divided Buildings
General
In Measure K a degree of protection for occupants is achieved by providing either a spatial separation or a fire separation
between two parts of the building as shown in Figures 11 and 12. Under these conditions, except as subsequently noted, air
pressures on either side of the division will be symmetrical and smoke should not pass from one side to the other. Smoke
from fire in one part of the building may be expected to pass into the stair shafts, elevator shafts and floor areas on the fire
side, while the equivalent spaces on the other side will remain smoke free. Vestibules and bridges are provided as means
of access to refuge areas for occupants of floor areas in the part of the building that is exposed to fire and smoke.
Vestibules or bridges are either vented to the outdoors or pressurized mechanically in order to prevent their acting as paths
for the transmission of smoke. In vented vestibules below the neutral pressure plane of the building, air will normally flow
from the vestibules to the floor areas and no smoke should enter the vestibules. In vestibules above the neutral pressure
plane, air will flow from the floor area to the vestibule and thence to the outdoors.
If a window breaks in the fire area, the pressure in the fire area will be the same as that in the vestibule and no smoke
transfer should occur. Where vestibules are mechanically pressurized, the air flow will always be from the vestibule to the
floor areas on either side, thus limiting the possibility of smoke entering the vestibule.
Provision of an opening to the outdoors at the foot of a stair shaft will increase the air pressure in the shaft in winter and
thus reduce the probability of entry of smoke from a floor on which a fire occurs.
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2024MMAH Supplementary Standard SB-4
Where a dividing wall is used to separate the two parts of a building (Figure 12), breakage of a window in a fire
compartment below the neutral pressure plane can be undesirable. The pressure in the fire compartment will increase to a
level approximately the same as exterior pressure, and this may cause substantial smoke flow through the dividing wall
from the fire side to the other side of the building. This consideration does not apply to a spatial separation as shown in
Figure 11. Provisions have been included to allow windows below the mid-height of a building on the side away from a
fire to be opened manually in order to bring the pressure in that space to the exterior pressure and to eliminate the pressure
difference across the dividing wall.
While the most efficient solution to the problem of moving occupants to a place of safety is to have bridges or connecting
vestibules at each floor level, the requirements in Measure K are that such bridges or vestibules should be at intervals of not
more than five storeys, and in the case of residential buildings more than 75 m high, the bridges or vestibules should be on
each storey. The approaches to the bridges or vestibules are by stairs and corridors whose width is controlled by Sentences
(6) and (7) of Measure K. These provisions combine to enable all occupants to reach a place of safety in about three
minutes.
Stack action and the operation of smoke control measures may produce pressures across certain doors that will interfere
with their normal operation. This may apply where a building has vestibules vented to the outdoors
(a) at any door that swings into a vestibule from a floor space farther below the mid-height of the building than the
distance shown in Graph 8 in Appendix A of this Supplementary Standard,
(b) at any door that swings out of a vestibule from a floor space that is farther above the mid-height of the building than
the distance shown in Graph 8 in Appendix A of this Supplementary Standard,
(c) at any door between a floor space and an elevator shaft that is farther above or below the mid-height of the building
than the distance shown in Graph 8 in Appendix A of this Supplementary Standard,
(d) at any door between a floor space and a stair shaft that is farther above grade than the height shown in Graph 8 in
Appendix A of this Supplementary Standard.
In a building that has vestibules that are pressurized, pressures that may interfere with the normal operation of doors may
occur with any door between a vestibule and a floor space where the rate of air injection exceeds 0.165 m3 /s for each
weatherstripped door, or 0.33 m3/s for each door that is not weatherstripped, and any door between a floor space and an
elevator shaft that is farther above or below the mid-height of the building than the height shown in Graph 8 in Appendix A
of this Supplementary Standard.
Where a mechanical air supply is required by Sentence (11) of Measure K, it may be desirable to heat the air supply and to
provide two air intakes in separate locations on the building face as discussed in the general provisions to Measures F and
G.
Where Measure K is adopted and a fire is detected by an automatic device or a manual pull station is actuated in a smoke
control region of the building, it is intended that a fire alarm will sound on all floors in that smoke control region, and that
the occupants on all floors will move through the dividing vestibules or bridges to the other smoke control region.
Measure K
(1) The requirements of measures to limit the movement of smoke in existing buildings may be met by incorporating
the requirements of Sentences (2) to (17).
(2) The building is designed as
(a) a structure divided into two smoke control regions by a continuous vertical fire separation that has a fire-resistance
rating not less than that required for a floor in Subsection 3.2.2. of Division B, or
(b) two or more smoke control regions separated by spatial separations that conform to the provisions of Subsection
3.2.3. of Division B.
(3) Bridges or vestibules are provided at intervals of not more than five storeys to permit movement of occupants from
one smoke control region to the other, except that in the case of residential buildings more than 75 m high, the bridges or
vestibules are located on each storey.
2024MMAH Supplementary Standard SB-4
(4) In each smoke control region referred to in Sentence (2), there is not less than one exit stair shaft and one elevator in
a shaft that meets the requirements of Article 3.2.6.5. of Division B and that is not common to both smoke control
regions.
(5) The floor area on either side of a bridge or vestibule is of sufficient size to accommodate its own normal population,
plus the occupants of the one to five storeys of the adjacent smoke control region who may have to enter the floor area
during a fire emergency, assuming 0.5 m2 per ambulatory person and 1.5 m2 per non-ambulatory person.
(6) The width of each bridge or vestibule and each connecting corridor and door on the same storey is sufficient to
provide not less than 3.67 mm of width for each person who may have to use these passages to reach the floor area
referred to in Sentence (5) from the adjacent smoke control region.
(7) The width of each stair or ramp that provides access to a floor having a bridge or vestibule from intervening floors is
sufficient to provide not less than 5.5 mm of width for each person who may have to use the stair to reach the bridge or
vestibule referred to in Sentence (6).
(8) Between each bridge or vestibule and public corridor is a fire separation that has a 45 min fire-resistance rating.
(9) Between each bridge or vestibule and a floor area other than the public corridor referred to in Sentence (8), is a fire
separation that has a fire-resistance rating as required for exits in Subsection 3.4.4. of Division B
(10) Each door opening into a bridge or vestibule conforms to Articles 3.4.6.10. and 3.4.6.11. of Division B and is
suitably identified as an access to an area of refuge.
(11) Each bridge or vestibule is provided with
(a) a vent opening to the outdoors that has an open area not less than 1 m2 and that may be provided with a closure that
is openable manually, or
(b) a mechanical air supply not less than that obtained from Graph 7 in Appendix A of this Supplementary Standard that
will be initiated as provided in Sentence (17).
(12) Where the building is divided into two smoke control regions by a fire separation as described in Clause (2)(a), each
floor area below the mid-height of each smoke control region is provided with a vent opening to the outdoors that has an
open area of not less than 1.5 m2 and that is normally closed but can be opened manually.
(13) Each stair shaft is vented to the outdoors as described in Sentence (4) of Measure A.
(14) Except as provided in Sentence (11), and except for exhaust from kitchens, washrooms and bathrooms in dwelling
units, air moving fans are stopped during a fire emergency in an air handling system that serves more than two storeys.
(15) Floor areas below the lowest exit storey are divided by a fire separation that has a fire-resistance rating not less than
that required in Clause (2)(a) and is in a location corresponding to the fire or spatial separations required for upper
storeys. Doorways protected by pressurized vestibules are provided in the separations as described in Clause (11)(b).
(16) Where a supply of air is required by Sentences (11) and (15), it is carried in ducts as described in Sentence (13) of
Measure F.
(17) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) closing doors in fire separations required by Sentences (8), (9) and (15) between floor areas and vestibules,
(b) initiating the mechanical air supply to the vestibules where required by Clause (11)(b) and Sentence (15), and
(c) stopping air handling systems where required by Sentence (14).
Page 48 • SB-4
2024MMAH Supplementary Standard SB-4
Measure L Areas of Refuge (smoke free areas)
General
Measure L is intended to provide refuge areas which occupants may enter during a fire. It may be used for buildings that
have many openings between floors so that it is impracticable to confine smoke to one floor level.
This measure is basically the same as described in Measure D, except that larger quantities of air must be injected into each
area of refuge than into a comparable vestibule in order to maintain tolerable conditions for the occupants. A typical floor
plan is shown in Figure 13. The area of refuge may include normally occupied space in the building, and because fire may
occur in one of these spaces, provision is made for alternative groups of areas of refuge.
Except in the case of Group C buildings more than 75 m high, areas of refuge may be provided on every fifth floor if the
access routes are made wide enough to allow all occupants to reach the area of refuge within three minutes (see Figure 14).
Stair shafts and elevators for firefighters must be protected on intermediate floors by vestibules or by pressurization of the
shafts.
Stack action and the operation of smoke control measures may produce pressures across certain doors that will interfere
with their normal operation. This may apply to any door between an area of refuge and a floor space that is farther above
grade than the height shown in Graph 8 in Appendix A of this Supplementary Standard.
Between every area of refuge and the floor space the building should have a vent fitted with a self-closing damper that will
permit air to move from the area of refuge to the floor space but not vice-versa. It should have an openable area not less
than 6 cm2 for every 0.005 m3/s of air injected into the area of refuge in excess of that specified in Measure D for a
pressurized vestibule.
Where Measure L is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is intended
that an alarm will sound on all floors simultaneously, and that occupants of all floors will move to areas of refuge
distributed throughout the building and await instructions over the voice communication system.
Where a mechanical air supply is required by Sentence (9) of Measure L, it may be desirable to heat the air supply and to
provide two air intakes in separate locations on the building face, as discussed in the general provisions to Measures F and
G.
Measure L
(1) The requirements of measures to limit the movement of smoke in existing buildings (except measures to limit the
movement from storeys below the lowest exit level into upper storeys) may be met by incorporating the requirements of
Sentences (2) to (20).
(2) Two independent groups of areas of refuge are distributed through the building so that there is an area of refuge in
each group at least at every fifth storey, and each group is linked by a common exit stair to the exterior at grade.
(3) On any floor area any area of refuge that has a door to an exit stair may also have a door to an elevator for
firefighters, but two exit stairs may not open on to the same area of refuge if no other vertical shaft is common to the two
independent systems described in Sentence (2).
(4) Each group of areas of refuge referred to in Sentence (2) can accommodate all the occupants of above grade storeys
at the rate of 0.5 m2 of floor area per ambulatory person or 1.5 m2 per non-ambulatory person.
(5) The width of corridors and doors leading to an area of refuge on the same storey is sufficient to provide 3.67 mm of
width for each person who may have to use these passages to reach the area of refuge.
(6) The width of stairs or ramps leading to an area of refuge from intervening floors is sufficient to provide 5.5 mm of
width for each person who may have to use the stairs or ramps to reach the area of refuge.
2024MMAH Supplementary Standard SB-4
(7) Between each area of refuge and a public corridor is a fire separation that has a 45 min fire-resistance rating.
(8) Between each area of refuge and a floor area other than the public corridor referred to in Sentence (7), is a fire
separation that has a fire-resistance rating as required for exits in Subsection 3.4.4. of Division B
(9) Each door opening into an area of refuge conforms to the provisions for doors in Article 3.4.6.10. of Division B and
is suitably identified as an access to an area of refuge.
(10) Each area of refuge is provided with a mechanical air supply not less than that required for a vestibule providing
access to a stair shaft or an elevator shaft in Clause (5)(b) of Measure D, and obtained from Graph 3 in Appendix A of
this Supplementary Standard, or not less than 0.002 m3/s for each occupant of the area of refuge during a fire emergency,
whichever is greater.
(11) Any door in an exit stair shaft or in a shaft that contains an elevator for firefighters that does not open directly into
an area of refuge is provided with a pressurized vestibule as described in Sentence (5) of Measure D, except where the
stair shaft or elevator shaft is pressurized as described in Sentences (2) and (4) of Measure F.
(12) Except as provided in Sentence (11), an elevator shaft that contains an elevator for firefighters is provided with a
pressurized vestibule as described in Sentences (2), (3) and (5) of Measure D or is pressurized as described in Sentence
(4) of Measure F.
(13) Any elevator shaft that contains an elevator for firefighters or opens into an area of refuge and passes through the
floor above the lowest exit storey does not penetrate the floor of the storey immediately below the lowest exit storey,
except where there is a vestibule between the elevator door or doors and each floor area below grade as described in
Sentence (3) of Measure D.
(14) A stair shaft serving storeys above the lowest exit level is vented to the outdoors at or near the bottom of the stair
shaft as described in Sentence (4) of Measure A.
(15) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(16) Each elevator shaft protected by a vestibule or area of refuge having a mechanical air supply as described in
Sentences (9) and (10) has a vent at or near the bottom of the shaft opening directly to the outdoors or into a vestibule or
corridor that has a similar opening to the outdoors having an openable area not less than 0.023 m2 for every door into the
shaft, other than doors at street floor level.
(17) The vent at the bottom of an elevator shaft referred to in Sentence (16) may be provided with a closure which is
openable manually and is designed to remain open during a fire emergency.
(18) Except for air moving fans serving areas of refuge and vestibules as provided in Sentences (10) to (12), and except
for exhaust from kitchens, washrooms and bathrooms in dwelling units, air moving fans are stopped during a fire
emergency in an air handling system that serves more than two storeys.
(19) Where a supply of air is required by Sentences (10), (11), (12) and (15), it is carried in ducts as described in
Sentence (14) of Measure F.
(20) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) closing doors in fire separations required by Sentences (7) and (8) between floor areas and areas of refuge or
vestibules,
(b) stopping air handling systems as required by Sentence (18),
(c) opening closures in vents to the outdoors in elevator shafts that may be required by Sentence (12), and
(d) initiating the mechanical air supply to the areas of refuge, vestibules and shafts as may be required by Sentences
(10), (11), (12) and (15).
Page 50 • SB-4
2024MMAH Supplementary Standard SB-4
Measure M Residential Buildings with Balconies
General
In residential buildings the greater part of the requirements for control of smoke movement are waived where each suite
has direct access to a balcony. The protective features are limited to stopping air handling systems, providing an opening
to the outdoors at the foot of stair shafts serving upper floors and protection of stair shafts in storeys below grade. A
typical arrangement is shown in Figure 16.
Where Measure M is adopted and a fire is detected by an automatic device or a manual pull station is actuated, it is
intended that occupants on the fire floor will evacuate if possible, and that occupants of other floors may remain in their
suites to await instructions.
Measure M
(1) The requirements specific to existing unsprinklered residential buildings may be met by incorporating the
requirements of Sentences (2) to (7).
(2) A stair shaft serving storeys above the lowest exit level has a vent or door to the outdoors at or near the bottom of
the stair shaft, as described in Sentence (4) of Measure A.
(3) A stairway serving storeys below the lowest exit level is protected as described in Sentence (3) of Measure A.
(4) Any elevator shaft that passes through the floor above the lowest exit storey does not penetrate the floor of the
storey immediately below the lowest exit storey, except where there is a vestibule between the elevator door or doors and
each floor area below grade as described in Sentence (3) of Measure D.
(5) Except for exhaust from kitchens, washrooms and bathrooms in dwelling units, air moving fans are stopped during a
fire emergency in an air handling system that serves more than two storeys.
(6) Where a supply of air is required by Sentence (3), it is carried in ducts as described in Sentence (13) of Measure F.
(7) The central alarm and control facility required by Article 3.2.6.7. of Division B is provided with additional controls
that are capable of
(a) stopping air handling systems as required by requirements specific to existing unsprinklered residential buildings,
and
(b) initiating the mechanical air supply to stair shafts as may be required by Clause (3)(c).
2024MMAH Supplementary Standard SB-4
Measure N Connected Buildings
General
The measures described here are intended to prevent movement of smoke from one building to another. They are of
particular significance where two buildings of unequal height are joined together. The techniques suggested are the
provision of a large opening to the outdoors in a connecting vestibule so that smoke entering through leakage areas around
doors will be vented to the outdoors, or pressurization to maintain a higher pressure in the vestibule than in adjacent spaces
as illustrated in Figures 17 to 19.
The requirements for protection of openings are described in terms appropriate to a doorway. Any other openings should
be avoided if possible. Where they occur, they should be protected by the provision of an air lock that gives the same
standard of protection as the vestibule described in Sentence (3).
Measure N
(1) The requirement of Sentence 3.2.6.3. of Division B that limits movement of smoke from one building to another
may be met by incorporating in the link between the buildings the requirements in Sentences (2) and (3).
(2) Between one building and the other is a firewall as described in Subsection 3.1.10. of Division B.
(3) Any opening in the firewall is protected against passage of smoke by a vestibule described in Sentence (3) of
Measure D and has
(a) a vent to the outdoors that has a net area of 10(0.023d + 0.00045a) m2, where d is the number of doors having a
perimeter not more than 6 m that open into the vestibule, or if the perimeter of doors exceeds 6 m, the value of d is
increased in direct proportion to the increase in the perimeter, and a is the area in square metres of enclosing walls,
floors and ceilings whose outer face is in contact with the outside air, except that where the outer face of a wall is in
contact with the ground or fill, it is assumed that there is no leakage through that portion, and the value of a is
assumed to be zero, or
(b) equipment capable of maintaining a supply of air into the vestibule sufficient to ensure that the air pressure in the
vestibule when the doors are closed is higher by at least 12 Pa than that in adjacent floor areas when the outdoor
temperature is equal to the January design temperature on a 2.5 percent basis.
Page 52 • SB-4
2024MMAH Supplementary Standard SB-4
Appendix A to SB-4
Graphs for Applying Smoke Control Measures
Graph 1 Graph 2
Vent to a vertical service space where no other shaft Vent to a vertical service space where other shafts
in the building is pressurized in the building are pressurized
Notes to Graphs 1 and 2:
(1) Curve A applies to a vertical service space that is enclosed by unplastered unit masonry or by plaster and steel stud construction with
all openings in the shaft sealed to the degree required by Articles 3.1.9.2. to 3.1.9.4. of Division B.
(2) Curve B applies to a vertical service space that is enclosed by monolithic concrete or by plastered unit masonry with all openings in
the shaft sealed tightly to minimize air leakage.
(3) A shaft having a vent that is 100 percent of the cross-sectional area of the shaft is acceptable for buildings up to 1.5 times the height
shown by the appropriate curve in Graphs 1 and 2.
(4) The total leakage area, based on measurements arrived at in typical high buildings, is assumed to be 0.025 m2 for every 10 m2 of shaft
wall area in the case of Curve A and 0.015 m2 for every 10 m2 of shaft wall area in the case of Curve B.
2024MMAH Supplementary Standard SB-4
Graph 3
Factor for mechanical air supply to a vestibule
Notes to Graph 3:
(1) The air supply to each vestibule in cubic metres per second equals
F3d + 0.071e + 0.094s
where
F3 is a factor obtained from Graph 3,
d = the number of doors having a perimeter not more than 6 m between each vestibule and a floor area,
e = the number of doors having a perimeter not more than 6 m between each vestibule and an elevator shaft, and
s = the number of doors having a perimeter not more than 6 m between each vestibule and a stair shaft. The quantity
"F3d + 0.071e + 0.094s" represents the total leakage from the vestibule.
(2) If the perimeter of a door exceeds 6 m, the value of d, e or s must be increased in direct proportion to the increase in the perimeter.
(3) A double leaf door is counted as two doors in this formula.
(4) A door provided with tight-fitting weatherstripping is counted as one half of a door.
(5) The height of the building is the number of metres between the roof and the floor level of the lowest basement floor.
Page 54 • SB-4
2024MMAH Supplementary Standard SB-4
Graph 4
Factor for air supply to an elevator shaft
Notes to Graph 4:
(1) The air supply to each elevator shaft in cubic metres per second equals
F4(0.023d4 + 0.0014a4)
where
F4 is the factor obtained from Graph 4
d4 = total number of doors having a perimeter not more than 6 m that open into the elevator shaft, and
a4 = area of enclosing walls of the shaft in square metres. The expression "0.023d4 + 0.0014a4" represents the total
leakage area in the walls of the shaft.
(2) If the perimeter of a door exceeds 6 m, the value of d4 must be increased in direct proportion to the increase in the perimeter.
(3) A double leaf door is counted as two doors in this formula.
(4) A door provided with tight-fitting weatherstripping is counted as one half of a door.
(5) If the enclosing walls of the shaft are of monolithic concrete or of unit masonry plastered on one side, the value of a4 may be halved.
(6) If an elevator shaft is provided with vestibules on each floor, the enclosing walls considered in this formula may be taken as including
those of the vestibules if it leads to an economy in air supply requirements. In this case d4 above refers to doors between the
vestibules and the floor areas and doors between the elevator shaft and the vestibules do not enter into the calculation.
2024MMAH Supplementary Standard SB-4
Graph 5
Factor for air supply for building pressurization
Notes to Graph 5:
(1) If Measure H is used, the air supply delivered to the whole building in cubic metres per second equals
F 5 x a5
where
F5 is a factor obtained from Graph 5, and
a5 = area of all exterior wall surfaces of the building in square metres measured between ground level and underside of
the roof. (Where the outer face of a wall is in direct contact with the ground or fill, it is assumed that there is no
leakage through that portion, and the value of a5 is assumed to be zero.)
(2) Graph 5 is based on an air leakage rate of 0.003 m3/s per square metre of exterior wall at a pressure difference of 75 kPa, based on
the measured leakage rate in high buildings having fixed windows and curtain wall panels.
(3) This is equivalent to a leakage area in exterior walls of 0.045 m2 per 100 m2 of wall area. If the leakage area in a building differs
significantly from this, the air supply should be adjusted in direct proportion.
(4) The height of building is measured between the underside of the roof and the floor level of the lowest basement floor.
(5) If Measure I or J is used, the air supply delivered to the space that includes stair shafts, elevator shafts and corridors in cubic metres
per second equals
F5(a6 + 51d6)
where
F5 is a factor obtained from Graph 5 that is not less than 0.0025,
a6 = area in square metres of the walls enclosing the space that includes stair shafts, elevator shafts and associated
corridors on all floors, and
d6 = total number of doors having a perimeter not more than 6 m in the wall area described in a 6.
(6) If the enclosing walls described above are of monolithic concrete or of unit masonry plastered on one side, the value of a6 may be
halved.
(7) If the perimeter of a door exceeds 6 m, the value of d6 must be increased in direct proportion to the increase in the perimeter.
(8) A double leaf door is counted as two doors in this formula.
(9) A door provided with tight-fitting weatherstripping is counted as a one half of a door.
Page 56 • SB-4
2024MMAH Supplementary Standard SB-4
Graph 6
Flow reduction factors
Graph 7
Air supply to vestibule in a vertically divided building
Notes to Graph 7:
(1) Curve A shows the air supply to each vestibule in cubic metres per second for a vestibule that has four doors (or two double doors),
each door having a perimeter of not more than 6 m, between the vestibule and the floor areas on either side of the building.
(2) Curve B shows the air supply to each vestibule in cubic metres per second for a vestibule that has two single doors, each door having
a perimeter of not more than 6 m, between the vestibule and the floor areas on either side of the building.
(3) If the perimeter of a door exceeds 6 m, the air supply must be increased in direct proportion to the increase in the perimeter.
(4) If the doors are provided with tight-fitting weatherstripping, the air supply may be halved.
(5) The height of building is the distance between the roof and the floor level of the lowest basement floor.
2024MMAH Supplementary Standard SB-4
Graph 8
Height of the shaft relative to grade, or the neutral pressure plane
at which pressure across a door may exceed 95 Pa
Page 58 • SB-4
2024MMAH Supplementary Standard SB-4
Appendix B to SB-4
Assumptions Used in Developing Fire Safety Measures
The objectives of the measures for fire safety in high buildings are
(a) to provide for the safety of the occupants of a building, either by maintaining the tenability of the occupied floor
spaces during the period of a fire emergency or by making it possible for occupants to move to a place of safety,
(b) to maintain tenable conditions in which occupants may remain in exit stairs leading from floor spaces to the
outdoors, and
(c) to maintain tenable conditions in elevators that can be used to transport firefighters and their equipment from the
street floor to the floor immediately below the fire floor.
It is assumed that the firefighters will use one of the protected stair shafts referred to in (b) to walk up to the fire floor from
the floor below.
The first of these objectives may be met by the evacuation of all occupants to the outdoors in from seven to ten minutes, by
the movement of occupants to safe areas within the building in from three to five minutes (as in Measures C, E, G, J, K, L
and M) or by maintaining the tenability of all floor areas except those on the fire floor and the floor above the fire floor (as
in Measures A, B, D, F, H and I).
The requirements in the Building Code covering widths of exits and travel distances to exits make it possible for occupants
of a floor on which a fire occurs to leave that floor within one or two minutes provided their escape route is not cut off by
the fire.
The objectives of the measures are to maintain certain spaces substantially smoke free for a significant period of time
during a fire emergency, and hence some criterion of tenability is called for. The criterion for long term tenability is that a
space shall not include more than one percent by volume of the contaminated atmosphere from the fire region. The
criterion of tenability is based on visibility and carbon monoxide concentration.
Mechanisms of Smoke Movement in Buildings
Movement of a smoky atmosphere within a building is not significantly different from that of a normal atmosphere at the
same temperature. The principal constituent of both atmospheres is nitrogen. The fact that the concentrations of other
component gases will differ and that a smoky atmosphere will contain particulate matter will not influence its overall
density to an extent that will significantly affect its movement. The mechanisms to be discussed do, therefore, relate to the
movement of a smoky atmosphere as well as a normal atmosphere.
Air Circulating Systems
An obvious mechanism for the dispersal of smoke within a building is the recirculating air handling system. Assuming that
the system has been competently designed, the approximate extent of the recirculation under any particular circumstances
is known, and hence the build-up in any area of contamination can be predicted.
Effect of Wind
Exterior winds create pressure differentials within buildings, which lead to internal air movement, principally horizontal.
Some upward movement also results, however, from the non-uniformity of the wind profile up the side of a building. In
addition, if one side of the building is facing the wind, only that face will be subjected to a positive pressure, the remainder
being subjected to negative pressure.
2024MMAH Supplementary Standard SB-4
Expansion
Another smoke movement mechanism, which is of considerable significance during the early stages of any fire that is not
well vented to the outdoors, is the expansion process associated with heating. The leakage characteristics of virtually any
building are such that the rate of temperature rise occurring in the fire region cannot create pressure differentials greater
than about 250 Pa (gauge). Instead, the volume of the atmosphere increases linearly with absolute temperature. During the
development of a fire in a compartment, absolute temperature may be expected to triple, and the volume of gas will
increase by approximately the same factor. At least two-thirds of the original atmosphere in the fire region will, therefore,
be displaced by this mechanism.
Generation of gases as a result of combustion has also been considered. The volume created by this phenomenon cannot,
however, exceed 20 percent of the original volume, and is not likely to be significant compared to expansion due to
temperature rise.
Stack Effect
Whenever a temperature differential exists between the interior and exterior of an enclosure, a phenomenon known as stack
or chimney effect prevails. Figure B-1 illustrates the case where the interior temperature is higher than the exterior, and
there is an inflow of cold air at low levels and a corresponding outflow at high levels.
Figure B-1
Stack action
This effect can result from building heating and from temperature differentials created by the fire itself and is particularly
important in Canadian buildings because of the cold winter conditions. The pressure differentials generated by stack effect
can be calculated by considering the densities of the internal and external atmospheres.
Figure B-1 represents a simplified model in which air flows in at a low level and out at a high level, while there is an
intermediate level where there is no pressure differential between interior and exterior. This level is referred to as "the
neutral pressure plane". Taking the pressure at the neutral plane as P0, the pressures at the lower or upper openings can be
derived, for they are associated with the weights of the columns of gas above them.
Page 60 • SB-4
2024MMAH Supplementary Standard SB-4
The resulting expression for the pressure difference across the lower opening is
δp = h1 gρθ θ/T0
where
δp = pressure difference,
h1 is defined in Figure B-1,
T0 = absolute outdoor temperature,
θ = difference between indoor and outdoor temperature,
ρθ = density of indoor air, and
g = acceleration due to gravity.
Substituting H = (h1 + h2) will give the total of the pressure head (the sum of the pressure differentials across the upper and
lower openings) generated by stack effect.
Importance of Mechanisms Responsible for Smoke Movement
Expansion due to heating of the atmosphere in a fire compartment is largely a transient phenomenon occurring at the
development stage of a fire. Two-thirds of the atmosphere of the fire region is likely to be displaced and, if the region were
not vented to the exterior, there could be a significant movement of smoke laden atmosphere to other parts of the building.
Dispersed evenly throughout the building, and taking into account leakage to outdoors, this displaced atmosphere could
render untenable a space equal to about 50 times that of the fire region.
Pressures Due to Stack Effect
In discussing the steady state conditions responsible for smoke movement, total pressure heads generated may be
compared. These pressure heads are tabulated in Table B-1 together with the flow rates that they will create beneath a
typical door having a free space of 900 mm x 12.5 m beneath it. In Columns 2 and 3, the total head given by stack action
resulting from a fire in a single storey is also given by stack action associated with building heating during cold weather in
a building three to four storeys high.
Table B-1
Magnitudes of Pressures Developed by Thermal and Wind Effects Magnitudes
Height of Heated Compartment, m
Flow Beneath Door with
Pressure Head, Pa 800°C above ambient Wind Speed, km/h
50°C above ambient 900 x 12.5 mm Gap, m3/s
(i.e., on fire)
25 2.9 10.3 23 0.045
50 5.8 20.6 33 0.064
125 14.5 51.6 52 0.1
250 29.1 103.3 73 0.142
500 58.2 206.4 104 0.201
Column 1 2 3 4 5
Assuming that a building is compartmented, fire other than one in a shaft should be confined to a single storey. The total
pressure head generated by the fire is thus not likely to exceed about 25 Pa. As buildings are generally heated in their
entirety, stack effect associated with building heating can give a total head significantly more than 25 Pa if the building is
more than about four storeys high. Thus combating stack action associated with building heating in high buildings is likely
to pose more of a problem than combating stack action directly associated with a fire. In high buildings emphasis should
be placed on the building heating rather than the fire stack action problem.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
Effect of Wind
Column 4 of Table B-1 indicates that pressures resulting from winds can be substantial. As mentioned earlier, the greater
part of the resulting airflow is horizontal. This does not create as great a hazard as vertical movement via the shafts in a
building. An upward flow does exist, however, and its effect is virtually identical to that of stack action associated with
building heating. Combating the latter will, therefore, take account of the more hazardous influence of winds.
Contribution of Air Handling Systems
The effect of recirculating air handling systems is not shown in Table B-1, but it is substantial and hence it must be
considered when smoke control techniques are being devised for buildings including such systems.
Significance of Smoke Movement Mechanisms
Given the considerations just discussed, the most significant smoke movement mechanisms to be combated are
(1) operating recirculating air-handling systems,
(2) the expansion process occurring during the initial stages of a fire, and
(3) stack action associated with building heating.
Techniques for Avoiding Widespread Smoke Contamination
Techniques for avoiding widespread smoke contamination in a high building can be divided into the following categories:
(1) Avoidance of any significant fire. The first approach in this category is to exclude or limit combustible materials
from a building. Calculations of air movement due to stack effect have indicated that the destruction by fire of very small
quantities of combustible material can produce enough smoke to produce untenable conditions in upper floors and vertical
shafts of a high building. Limits on the use of smoke producing materials are thus unlikely to be adequate as a sole means
of smoke control. Automatic extinguishment of a fire can also be considered as an approach to limiting smoke generation
provided the quantity of combustibles destroyed is held within strict limits.
(2) Compartmentation. Where a floor area is divided into a number of fire compartments, the potential size of a fire
will be limited to the contents of one compartment. In addition there will be, in some circumstances, dilution of smoke
moving from the fire compartment to other floors.
Where the fire occurs below the neutral plane, in cold weather the path of smoke travel may be along a corridor to stair
shafts and elevator shafts. In this case the smoke in the corridor will be diluted by clean air coming from other
compartments. In an ideal situation (uniform compartments, no expansion and no wind), dilution of the smoke laden air
will be in proportion to the number of compartments. Breaking of a window in the fire compartment will, however,
increase the pressure in that space and will reduce the effect of dilution.
Where smoke travel occurs through a vertical shaft from a compartment involved in fire to higher compartments, the level
of contamination will not be related to the number of units on one floor, but will likely be restricted to units on other floors
that are adjacent to the vertical shaft.
The result of compartmentation is, therefore, likely to be beneficial, but does not eliminate the need for smoke control
measures.
(3) Location of shafts outside the building envelope. The vertical transfer of smoke to the upper storeys of a
building from fire on a lower storey occurs largely by the vertical shafts in the building rather than through the floors, about
95 percent or more in the case of a typical 20-storey building. Separation of the shafts from the building would thus largely
solve the problem. This approach constitutes one of the suggested methods of smoke control.
(4) Dilution. Dilution by a factor of about 100 of the smoke gases issuing from a fire region will provide a tenable
atmosphere. This feature could form the basis of a smoke control method, air being injected into the building at
appropriate rates at those locations where smoke is being discharged from the fire region into adjacent parts of the building.
Page 62 • SB-4
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
2024MMAH Supplementary Standard SB-4
When cold weather conditions are considered, however, dilution alone is not likely to be very practical. In general, it
would be better if the injection of air were directed to modifying the pressure pattern within a building in order to limit any
undesirable movement of smoke.
Dilution as a means of reducing smoke contamination should, nevertheless, be considered as an important secondary factor
governing a designer's choice of smoke control method. Its importance is in dispersing contamination that might develop
as a result of delay in implementing smoke control measures, or of other occurrences such as the opening of a number of
doors that might interfere with the operation of a smoke control measure. The amount of air required to dilute a
contaminated atmosphere to a tenable level can be calculated approximately. If no mixing were to occur between the
contaminated and the clean air, and the contaminated air were to move out ahead of the clean air, one volume of the clean
air injected into a compartment would produce a smoke free atmosphere. In practice, however, some mixing does occur.
If perfect mixing is assumed in a compartment that has reached a level of contamination equivalent to that of the fire
compartment, and no more smoke is entering, the amount of clean air needed to create the one percent tenable atmosphere
discussed would be five times the volume of the compartment. If, however, we are considering a compartment isolated
from the fire compartment by a fire separation and self-closing doors, it is more reasonable to assume that the level of
contamination likely to occur is about one-fifth of that in the fire compartment. In these circumstances, injection of three
volumes of clean air would be sufficient to produce a tenable atmosphere. If clean air is injected at the rate of one volume
every two minutes, the atmosphere in the compartment would be satisfactory in about six minutes.
These figures are based on the expression
c = c0eat
where
c0 = initial concentration of contaminant,
c = final concentration of contaminant,
a = rate of diluent air flow in number of air changes per minute,
t = time in minutes between occurrence of initial and final concentration, and
e = 2.718.
Based on this calculation, assuming perfect mixing of the contaminated air and the diluent air,
c/c0 = 0.368 after injection of one volume of clean air,
0.135 after injection of two volumes of clean air,
0.050 after injection of three volumes of clean air,
0.018 after injection of four volumes of clean air, and
0.007 after injection of five volumes of clean air.
(5) Adjustment of pressure differential distribution. This category of smoke control technique involves
modification of the pressure pattern within the building. The pressure distribution within a building is illustrated by the
pressure characteristic diagrams in Figure B-2. The graphs represent, in an exaggerated manner, the pressure differences
between floor areas, shafts and exterior at the same height above ground. The pressure difference shown amounts to little
more than 500 Pa, whereas the total pressures involved are about 100 kPa. The graphs do relate pressure to heights, and
thus cannot be used to determine pressure difference between one floor and another at a different height. Given any set of
characteristics as in Figure B-2, the important feature is that, during cold weather, air flow from one region to another at the
same level will be towards the region that is at a lower pressure. In the typical building whose characteristics are
illustrated, smoke generated at a low level will flow into shafts, up through the shafts and out into floor spaces at the higher
levels.
2024MMAH Supplementary Standard SB-4
Figure B-2
Pressure characteristics of a typical building
Shafts provide the major paths for the spread of smoke within a building, so one should note the effect of venting on their
characteristics. Figure B-3 shows the characteristics of a simple heated shaft under three different venting arrangements,
the second and third (Figures B-3(b) and B-3(c)) having obvious advantages in controlling smoke movement in buildings.
In Figure B-3(b) the shaft is vented to the outdoors at the top, and smoke entering the shaft at any level would not leave it
until it reached the top opening. If a corresponding condition were established within a building, the shaft would,
therefore, not constitute a path for the transmission of smoke from low level to high level floor spaces. In Figure B-3(c) the
shaft is vented to the outdoors at the bottom, fresh air enters the shaft at the lowest level and leaves it through any leakage
area at any other level in the shaft. Such a condition for a shaft in a building would be most valuable, for as well as being
eliminated as a path for smoke dispersal, the shaft also has a clear atmosphere. These conditions, however, may not be
sustained long as the atmosphere in the shaft will cool as a result of the influx of cold air, and the characteristic will
approach that of the exterior atmosphere. Injection of warm air into the shaft is necessary to maintain these conditions over
a prolonged period.
Where a smoke control method is concerned with changing the pressure pattern within a building, many of the measures
involved are based on the preceding concept of changing the pressure characteristic of a shaft. Since shafts are the
principal paths by which smoke disperses throughout a building, the aim will be either to decrease or to increase shaft
pressures substantially. Both measures will eliminate vertical smoke transfer by the shaft between floor spaces. Top
venting the shaft as in Figure B-3(b) or use of mechanical exhaust to approach these pressure characteristics will, however,
also result in the entry of smoke into the shaft, while pressurizing the shaft, such as by mechanical injection, will maintain a
tenable atmosphere in the shaft.
Page 64 • SB-4
2024MMAH Supplementary Standard SB-4
Figure B-3
Shaft characteristics
(6) Smoke shafts. A smoke shaft differs from a vented service shaft in that an opening is provided into the shaft from
the fire floor in addition to the opening to the outside at the top of the shaft.
Until windows in outer walls are broken, a smoke shaft alone can be an effective means of limiting movement of smoke
into other floors and shafts. In cold weather, the shaft air is warmer than the outdoor air and the shaft will begin to function
as a vent as soon as the dampers are opened. During warm weather there will be some delay, as the smoke shaft cannot
function as a vent until hot air has entered the shaft as a result of initial expansion in the fire region. The pressure
conditions that prevail during cold weather are shown in Figure B-4. The air pressure on the fire floor, having an opening
into the smoke shaft, is below that in adjacent unvented shafts and adjacent floor areas. Air flow will be from the adjacent
floor areas and shafts into the fire floor, and from the fire floor into the smoke shaft. If, however, a window is broken on a
fire floor at a lower level, the air pressure in the fire region will be increased to approximately that of outdoor air at the
same level. Smoke may then flow into stair shafts and elevator shafts and adjacent floor areas. During warm weather,
breaking of a window will allow venting of smoke to the outdoors for a fire on any floor, except when wind is blowing
towards the open window. In this event, breaking of the window will cause the action of the smoke shaft to be
overwhelmed. The smoke shaft, therefore, is not fully effective as a sole method of smoke control in a floor area with
windows, but can be used in conjunction with building pressurization as part of a smoke control method. The size of a
smoke shaft is related to conditions to be established in the event of a fire at a lower level of the building and is dependent
on the leakage characteristics of the building. Any increase in the air leakage through the walls of the building and the
shafts requires a corresponding increase in the size of the smoke shaft. In Figure B-4 the idealized smoke shaft pressure
characteristic is indicated by a dotted line and assumes no pressure losses inside the shaft. As the smoke shaft is open to
the outside at the top, pressure at the top level of the smoke shaft is equal to that of outside air.
2024MMAH Supplementary Standard SB-4
Figure B-4
Pressure differences produced by a smoke shaft
Assuming an air temperature inside a smoke shaft equal to that of the building, as may occur in the case of a small fire, the
slope of the smoke shaft pressure characteristic is the same as those of the vented shafts. In Figure B-4 the total pressure
(DPT) acting across the vent opening at the bottom is represented by the horizontal distance between floor space and
smoke shaft pressure characteristics. The value of DPT is about one half of the total pressure head generated by stack
action over the height of the building. The values of DPT are plotted against building height for various outside
temperatures in Figure B-5. The movement of air through the smoke shaft causes a decrease in building pressures, which
results in the shifting of the floor space pressure characteristic to the left in the pressure diagram. This results in a lower
effective value of DPT. The values of DPT have been adjusted to take this factor into account. So far it has been assumed
that no pressure losses occur inside the smoke shaft. Friction, momentum and dynamic pressure losses can, however, occur
inside the smoke shaft, as a result of air flow through the open vent of the fire floor, as well as through leakage openings in
the walls of the smoke shaft. The smoke shaft pressure characteristic including pressure losses is also shown in Figure B-4
as a solid line. The actual pressure difference across the open smoke vent DPv is less than DPT, the difference between the
two values representing the pressure losses inside the smoke shaft. The flow requirement to achieve the desired venting
action depends on the pressure differences across the fire floor enclosure caused by stack action, and on the air tightness of
the various interior and exterior separations of the building. The flow rates shown in Figure B-6 were calculated initially
for a 20-storey building having a floor plan measuring 36 m by 36 m, with assumed leakage through walls and floors
consistent with the results of air movement measurement obtained in several multi-storey buildings. Extrapolation was
made for buildings of various heights, floor areas and outside temperatures using the following relationships:
(1) QV is proportional to FA,
(2) QV is proportional to H1/2, and
(3) QV is proportional to
(Ti − To )1 / 2
To
where
QV is the required flow rate through the floor vent of the smoke shaft, FA is the flow area of a typical floor,
H is the height of building,
Ti is the indoor absolute temperature, and
To is the outdoor absolute temperature.
A number of other considerations may have to be taken into account in applying measures for control of smoke movement.
Page 66 • SB-4
2024MMAH Supplementary Standard SB-4
Figure B-5
Available total pressure versus building height
Figure B-6
Required venting capacity of smoke shaft
(7) Make-up air. In the case of smoke control systems that depend on a supply of make-up air from outside the
building for pressurization or dilution, the air intakes should be located so that there is little possibility of smoke or other
products of combustion being drawn into the air handling system. The source of the smoke could be a fire in the building.
The smoke could reach the air intakes as a result of siting the intakes close to the discharge from a smoke shaft or as a
result of wind patterns directing smoke that has been vented out through the building envelope towards the intakes. Other
sources of smoke are vents from fuel fired equipment, including furnaces and emergency electricity generators, and fire in
an adjacent part of a building separated from the building under consideration by fire separations and vestibules, as would
occur in the use of Measure K. Air intakes located near ground level should be sited so that exhausts from emergency and
other vehicles are not likely to be drawn into the air handling system.
2024MMAH Supplementary Standard SB-4
Breaking of Windows on the Fire Floor
Where the room in which a fire occurs has windows, they will probably be broken at a fairly early stage. This will result in
a change of pressure in the fire region to substantially that of outdoor air pressure at that level. In Figure B-2, for a fire at a
low level in the building during cold weather, breaking of windows will greatly increase the pressure in the region
involved. As a result more smoke may be expected to pass into adjacent floors and vertical shafts. This has been taken
into consideration in the measures described in Section 3.
Pressures Across Doors
Problems may occur where air pressures across typical hinged doors and sliding elevator doors interfere with their normal
use. This may occur when the pressure across a door exceeds 100 Pa. Pressure differences of this magnitude may occur in
cold weather where a door communicates with a space that is substantially at outdoor air pressure. This commonly occurs
at the entrance doors to high buildings during normal use. The problem is resolved in this case by use of revolving doors or
by special hinges which permit the door to rotate about the centre until a sufficient opening is formed to relieve the
pressure on the door. It may also occur when windows on a fire floor are broken or where vestibules vented to the outdoors
are employed, as in Measure D in Section 3. Situations where such problems may arise are indicated in the explanatory
notes to each smoke control measure.
Explosions in Smoke Shafts
An explosion may occur in a smoke shaft during a fire. The maximum over-pressure predicted on the basis of a British
report would probably not exceed about 16.5°C. This has been considered, and because it is a somewhat remote
possibility, no special precautions are recommended.
Pressure Drop in Stairs
Recent studies have shown that air supply requirements for stairwells with an open door at grade level can cause a
substantial pressure drop due to friction. If the air is injected only at the top of particular designs of stairwell in a high
building, a non-uniform pressure distribution over the height of the stair shaft may occur. This may produce an undesirably
high pressure differential across stairwell doors at high levels. This problem may be avoided by injection of the air at
several levels rather than only at the top.
Warm Weather Conditions
The smoke control techniques have been developed to function under cold weather conditions; their performance under
warm weather conditions has, however, been carefully considered. Undesirable pressures may be created across certain
doors, and certain spaces such as a stair shaft may be contaminated when the door to the outdoors is open. Where air
injection is used, modulation of the supply with exterior temperature can be a solution to the problem, although such action
reduces the effect of the air supply in diluting transient smoke contamination. Where no interior-exterior temperature
differential exists, building heating does not cause stack action and its influence as a smoke movement mechanism
disappears. Assuming air handling systems to be shut down, expansion becomes a major factor in spreading smoke
throughout a building. Under these conditions the influence of a simple vent opening in an external wall can be readily
assessed. Flow through all openings in the walls around the fire region will be roughly in proportion to their area. If the
area of the vent to the exterior is ten times the area of the openings communicating to the remainder of the building, only
about ten percent of the displaced smoke laden atmosphere will pass into other parts of the building.
During cold weather, expansion may be responsible for a slight overall increase in pressure of about 25 Pa in the fire region
for about 20 minutes.
Page 68 • SB-4
2024MMAH Supplementary Standard SB-4
Appendix C to SB-4
Check of a Smoke Control System
The efficiency of a smoke control system may be checked by measuring pressure differences and the directions of air flow
around doors and through separating walls of compartments. A pressure meter can be used to measure pressure differences
on either side of a door or partition. Where this is impracticable, a punk stick held near a crack will give an indication of
the direction of air flow. Measurements of air flow may be taken on the intake side of supply fans or in supply ducts to
determine whether the specified air flow is being provided.
In general, air flow should be from the spaces which may be occupied during a fire emergency (e.g., stair shafts) toward the
space in which the fire is assumed to have occurred. For each method of smoke control, measurements may be taken at
certain critical locations to check the overall efficiency of the system.
In buildings designed by Measure B, C, D or E, where protection is obtained by venting corridors or vestibules to the
outdoors, inspection of the building to determine whether the requirements have been met should be sufficient. In
buildings incorporating Measure B, C, D, E, F or G, service shafts may be vented to the outdoors at the top. In this case a
check may be made of the wall between the shaft and the uppermost occupied floor areas, to ensure that the direction of
flow is from each floor area into the shaft, when the vent to the outside is open and the outdoor air temperature is
significantly less than that indoors. In a building incorporating Measure D or E, where mechanically pressurized vestibules
are used, and in a building incorporating Measure L, a check may be made to ensure that the pressure in each vestibule or
area of refuge is greater than that in the adjacent floor areas at each floor level.
In a building incorporating Measure F or G, the efficiency of a protected elevator shaft can be checked by using a meter to
measure pressure differences between the shaft and the outdoors at grade, before and after actuation of the air injection
system. The difference between the two readings gives the mechanical pressurization of the shaft, which should be at least
equal to one half of the calculated pressure difference caused by stack action over the height of a building for the January
design temperature and the design flow rate specified in Sentence (4) of Measure F or Sentence (4) of Measure G. Where
the air flow is modulated, the mechanical pressurization should vary between 50 Pa when the outdoor temperature is equal
to that indoors, and one half of the pressure difference noted above when the outdoor temperature is equal to the January
design temperature. Flow rates into the elevator shaft may be checked against that specified in Sentence (4) of Measure F
and Sentence (4) of Measure G. Stair shafts may be checked with the air injection system operating and the door or vent to
the outdoors open. Flow rate through the shaft should be equal to that required by Sentence (2) of Measure F and Sentence
(2) of Measure G. Top vented service shafts may be checked as described for a building incorporating Measure B, C, D or
E.
In a building incorporating Measure H, the efficiency of the system may be checked by measuring pressure differences
between floor areas at grade and outdoors before and after actuation of the air injection system. The magnitude of the
mechanical pressurization is obtained as described above in the case of elevator shafts in a building incorporating Measure
F or G and should be equal to half the pressure difference caused by stack action over the height of the building for the
January design temperature and the design flow rate specified in Sentence (2) of Measure H. The effect of modulating air
flow for different temperature conditions is also as described for elevator shafts. Flow rates into the building may be
checked against those required in Sentence (2) of Measure H. A check may be made on each floor individually, with the
air injection system operating and the damper to the smoke shaft or panel to the outdoors open. Under these circumstances,
air flow should be from the stair shafts, elevator shafts and service shafts into the floor area that has a damper or panel
open.
In a building incorporating Measure I or J, pressure differences should be measured between the central core at grade and a
suite that has a number of windows open to the outdoors before and after actuation of the air injection system. The
magnitude of mechanical pressurization is obtained as described above in the case of elevator shafts in a building
incorporating Measure F or G and should be equal to one half of the pressure difference caused by stack action over the
height of the building for the January design temperature and design flow rate specified in Sentence (2) of Measure I. The
effect of modulating air flow for different temperature conditions is also as described for elevator shafts. Flow rates into
the central core may be checked against those required in Sentence (2) of Measure I.
2024MMAH Supplementary Standard SB-4
In a building incorporating Measure K, inspection should indicate whether or not there is a continuous separation between
two parts of the building, extending from the roof through storeys below grade. Where pressurized vestibules are used, a
check may be made to ensure that the direction of air flow is from each vestibule into adjacent floor areas at each level.
The check should also be made on a low level floor with the floor space vents referred to in Sentence (12) of Measure K, or
other windows in the two halves of the building open on that floor. This represents the condition when the fire has broken
windows in one half of the building and the compensating vent in the other half of the building has been opened manually.
In a building incorporating Measure L, the method of checking is the same as in a building incorporating Measure D or E,
except that flow rates into areas of refuge should be measured to ensure that they meet the requirements of Sentence (9) of
Measure L.
Doors to stair shafts, elevator shafts and vestibules that are indicated in the notes relating to each measure as being in
locations subject to pressure differences that may interfere with normal opening should be checked when the outdoor
temperature is near the January design temperature, with the air injection system operating and a number of windows open
to the outdoors on each floor in turn.
References
General
(1) High-Rise Building Fires and Fire Safety. Fire Journal and Fire Technology, NFPA No. SPP-18, 1972, 164 pp.
(2) N.B. Hutcheon, Safety in Buildings. CBD 114, Division of Building Research, National Research Council Canada,
Ottawa, June 1969.
(3) M. Galbreath, Fire in High Buildings. DBR Fire Study No. 21, Division of Building Research, National Research
Council Canada, Ottawa, April 1968. NRCC 10081.
(4) G.W. Shorter, Fire in Tall Buildings. Fire Fighting in Canada, October 1967.
Evacuation
(5) M. Galbreath, Time of Evacuation by Stairs in High Buildings. Fire Fighting in Canada, February 1969.
(6) J.L. Pauls, Evacuation and Other Fire Safety Measures in High-Rise Buildings. ASHRAE Trans., Vol. 81, Part 1, 1975,
pp. 528-533.
Smoke Movement and Control (General)
(7) A.G. Wilson and G.W. Shorter, Fire and High Buildings. Fire Technology, Vol. 6, No. 4, November 1970,
pp. 292-304. NRCC 11789.
(8) J.H. McGuire, G.T. Tamura and A.G. Wilson, Factors in Controlling Smoke in High Buildings. ASHRAE Symposium
Bulletin, January 1970, pp. 8-13. NRCC 12016.
(9) N.B. Hutcheon and G.W. Shorter, Smoke Problems in High-Rise Buildings. ASHRAE Journal, Vol. 10, No. 9,
September 1968, pp. 57-61. NRCC 10427.
(10) J.H. McGuire and G.T. Tamura, Smoke Control in High-Rise Buildings. CBD 134, Division of Building Research,
National Research Council Canada, Ottawa, February 1971.
(11) G.T. Tamura and J.H. McGuire, Smoke Movement in High-Rise Buildings. CBD 133, Division of Building Research,
National Research Council Canada, Ottawa, January 1971.
(12) J.H. McGuire and G.T. Tamura, The National Building Code Smoke Control Measures - An Overview. Engineering
Digest, Vol. 25, No. 9, October 1979, pp. 35-38. NRCC 17920.
Page 70 • SB-4
2024MMAH Supplementary Standard SB-4
(13) G.T. Tamura, Review of the DBR/NRC Studies on Control of Smoke from a Fire in High Buildings. ASHRAE Trans.
Vol. 89, Part 1B, 1983, pp. 341-361. NRCC 23054.
(14) G.T. Tamura, Smoke-Control Systems in High-Rise Buildings, 1976-1980 Survey. Engineering Digest, Vol. 30,
No. 7, August 1984, pp. 32-34. NRCC 23874 .
(15) G.T. Tamura and P.J. Manley, Smoke Movement Studies in a 15-Storey Hotel. ASHRAE Trans., Vol. 91,
Part 2B, 1985, pp. 1237-1253. NRCC 26359.
(16) J.H. McGuire and G.T. Tamura, Simple Analysis of Smoke-Flow Problems in High Buildings. Fire Technology, Vol.
11, No. 1, February 1975, pp. 15-22. NRCC 14773.
Specialized Aspects of Smoke Control
(17) G.T. Tamura and C.Y. Shaw, Basis for the Design of Smoke Shafts. Fire Technology, Vol. 9, No. 3, August 1973, pp.
209-222. NRCC 13851.
(18) G.T. Tamura and A.G. Wilson, Natural Venting to Control Smoke Movement in Buildings via Vertical Shafts.
ASHRAE Trans., Vol. 76, Part II, 1970, pp. 279-289. NRCC 12357.
(19) G.T. Tamura, Analysis of Smoke Shafts for Control of Smoke Movement in Buildings. ASHRAE Trans., Vol. 76, Part
II, 1970, pp. 290-297. NRCC 12356 .
(20) G.T. Tamura, J.H. McGuire and A.G. Wilson, Air-Handling Systems for Control of Smoke Movement. ASHRAE
Symposium Bulletin, January 1970, pp. 14-19. NRCC 12017.
(21) N.B. Hutcheon, Fire Protection in Air System Installations. Heating, Piping and Air Conditioning, Vol. 40, No. 12,
December 1968, p. 102. NRCC 10545.
(22) G.T. Tamura and C.Y. Shaw, Experimental Studies of Mechanical Venting for Smoke Control in Tall Office Buildings.
ASHRAE Trans., Vol. 84, Part 1, 1978, pp. 54-71. NRCC 17234.
(23) G.T. Tamura, Experimental Studies on Exterior Wall Venting for Smoke Control in Tall Office Buildings. ASHRAE
Trans., Vol. 84, Part 2, 1978, pp. 204-215. NRCC 17279.
(24) G.T. Tamura, The Performance of a Vestibule Pressurization for the Protection of Escape Routes of a 17-Storey Hotel.
ASHRAE Trans., Vol. 86, Part 1, 1980, pp. 593-603. NRCC 19017.
(25) G.T. Tamura and C.Y. Shaw, Field Check on the Building Pressurization Method for Smoke Control in High-Rise
Buildings. ASHRAE Journal, Vol. 23, No. 2, February 1981, pp. 21-25. NRCC 19199.
(26) G.T. Tamura, A Smoke Control System for High-Rise Office Buildings. ASHRAE Journal, Vol. 24, No. 5, May 1982,
pp. 29-32. NRCC 20317.
(27) G.T. Tamura and K. Tsuji, Simplified Method for Designing a Mechanical Smoke Exhaust System for High-Rise
Buildings. ASHRAE Trans., Vol. 91, Part 2 B, 1985, pp. 642-656. NRCC 26341.
(28) G.T. Tamura, Experimental Studies on Pressurized Escape Routes. ASHRAE Trans., Vol. 80, Part 2, 1974,
pp. 224-237. NRCC 14566.
(29) G.T. Tamura and J.H. Klote, Experimental Fire Tower Studies of Elevator Pressurization Systems for Smoke Control.
ASHRAE Trans. Vol. 93, Part 2, 1987. NRCC 29121.
(30) J.H. Klote and G.T. Tamura, Experiments of Piston Effect on Elevator Smoke Control. ASHRAE Trans. Vol. 93, Part
2, 1987. NRCC 29120.
2024MMAH Supplementary Standard SB-4
Computer Studies
(31) H. Yoshida, C.Y. Shaw and G.T. Tamura, A Fortran IV Program to Calculate Smoke Concentrations in a Multi-Storey
Building. Computer Program No. 45, Division of Building Research, National Research Council Canada, Ottawa, June
1979.
(32) G.T. Tamura, Computer Analysis of Smoke Control with Building Air Handling Systems. ASHRAE Journal, Vol. 14,
No. 8, August 1972, pp. 46-54. NRCC 12809.
(33) C.Y. Shaw and G.T. Tamura, Fortran IV Programs for Calculating Sizes and Venting Capacities of Smoke Shafts.
Computer Program No. 36, Division of Building Research, National Research Council Canada, Ottawa, June 1973 .
(34) G.T. Tamura, Computer Analysis of Smoke Movement in Tall Buildings. ASHRAE Trans., Vol. 75, Part II, 1969, pp.
81-92. NRCC 11542.
Air Leakage Studies
(35) C.Y. Shaw, D.M. Sander and G.T. Tamura, Air Leakage Measurements of the Exterior Walls of Tall Buildings.
ASHRAE Trans., Vol. 79, Part II, 1973, pp. 40-48. NRCC 13951.
(36) G.T. Tamura and A.G. Wilson, Pressure Differences Caused by Wind on Two Tall Buildings. ASHRAE Trans.,
Vol. 74, Part II, 1968, pp. 170-181. NRCC 10628.
(37) G.T. Tamura and A.G. Wilson, Pressure Differences Caused by Chimney Effect in Three High Buildings and Building
Pressures Caused by Chimney Action and Mechanical Ventilation. ASHRAE Trans., Vol. 73, Part II, 1967. NRCC
9950 .
(38) G.T. Tamura and A.G. Wilson, Pressure Differences for a Nine-Storey Building as a Result of Chimney Effect and
Ventilation System Operation. ASHRAE Trans., Vol. 72, Part I, 1966, pp. 180-189. NRCC 9467.
(39) G.T. Tamura and C.Y. Shaw, Air Leakage Data for the Design of Elevator and Stair shaft Pressurization Systems.
ASHRAE Trans., Vol. 82, Part II, 1976, pp. 179-190. NRCC 15921.
Associated Elementary Theory
(40) A.G. Wilson and G.T. Tamura, Stack Effect and Building Design. CBD 107, Division of Building Research, National
Research Council Canada, Ottawa, November 1968.
(41) A.G. Wilson and G.T. Tamura, Stack Effect in Buildings. CBD 104, Division of Building Research, National Research
Council Canada, Ottawa, August 1968.
Page 72 • SB-4
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2024MMAH Supplementary Standard SB-5
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MMAH Supplementary Standard SB-6
MMAH Supplementary Standard SB-6
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COMMENCEMENT
MMAH Supplementary Standard SB-6 comes into force on the 1st day of January 2025.
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