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OBC DIVISION B · PART 3 · SECTION 3.2 — FUNCTIONAL STATEMENTS / BUILDING FIRE SAFETY

When is a fire alarm system required in a building in Ontario?

A fire alarm system is generally required in buildings more than three storeys, buildings with an occupant load over 300, buildings with sleeping accommodation for more than 10 people, and in sprinklered buildings, among other triggers.

Code reference
The Code lists conditions requiring a fire alarm system, including building height above three storeys, total occupant load above thresholds, sleeping occupancies beyond a small size, contained-use and care occupancies, and buildings with required sprinkler or standpipe systems. It also governs single-stage versus two-stage operation, detector and pull station placement, annunciation and signal audibility.
OBC Division B, Subsection 3.2.4.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

Once a system is required, the design cascades: smoke detectors in specific rooms and shafts, heat detection, annunciator panels near the principal entrance, and audibility levels in suites, which often means in-suite sounders for residential. High buildings and care occupancies typically need two-stage voice-capable systems. A common pitfall is treating the fire alarm as an electrical afterthought; verification to CAN/ULC-S537 and integration with sprinklers, magnetic hold-opens and elevators need early coordination.

Plain language

Taller buildings, buildings where lots of people gather, and buildings where people sleep need an electric fire alarm system with pull stations, detectors and horns loud enough to wake everyone, all connected so the whole building is warned at once.

Related questions

When is noncombustible construction required under the Ontario Building Code?When are automatic sprinklers required in a building in Ontario?What are the fire department access route requirements under the Ontario Building Code?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.