PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code
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9.33.6.2.Materials in Air Duct Systems
(1) Except as provided in Sentences (2) to (6.2) and in Article 3.6.4.3., all ducts, duct connectors, associated fittings and
plenums used in air duct systems shall be constructed of steel, aluminum alloy, copper, clay or similar noncombustible
material.
(2) Ducts, associated fittings and plenums are permitted to contain combustible material provided they
(a) conform to the appropriate requirements for Class 1 duct materials in CAN/ULC-S110, “Standard Methods of Test
for Air Ducts,”
(b) conform to Article 3.1.5.18. and Subsection 3.1.9.,
(c) are not used in vertical runs serving more than 2 storeys, and
(d) are not used in air duct systems in which the air temperature may exceed 120°C.
(3) Duct sealants shall have a flame-spread rating of not more than 25 and a smoke developed classification of not more
than 50.
(4) Duct connectors that contain combustible materials and that are used between ducts and air outlet units shall
(a) conform to the appropriate requirements for Class 1 air duct materials in CAN/ULC-S110, “Standard Methods of
Test for Air Ducts,”
(b) be limited to 4 m in length,
(c) be used only in horizontal runs, and
(d) not penetrate required fire separations.
(5) Combustible ducts that are part of a duct system carrying only ventilation air and that are contained entirely within a
dwelling unit need not comply with the requirements of Sentences (1) to (4).
(6) Except as provided in Sentences 9.33.6.13.(2) and (3), ducts that are part of a return-air duct system and that are
contained entirely within a dwelling unit need not comply with the requirements of Sentences (1) to (4).
(6.1) All ductwork and fittings shall be constructed and installed in conformance with SMACNA Manuals and ASHRAE
Handbooks.
(6.2) All duct materials and fittings shall be
(a) suitable for exposure to the temperature and humidity of the air being conveyed, and
(b) resistant to corrosion due to contaminants in the air being conveyed in the duct.
(7) Materials referred to in Sentences (1) to (6.2), when used in a location where they may be subjected to excessive
moisture, shall
(a) have no appreciable loss of strength when wet, and
(b) be corrosion-resistant
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.