Carbon Monoxide Alarm Requirements in Ontario: What Every Building Owner Must Know in 2026

Carbon monoxide is invisible, odourless, and kills without warning. It is responsible for more accidental poisoning deaths in Canada than any other substance. In Ontario, the law requires CO alarms in a wide range of buildings — yet compliance gaps remain common, particularly in older multi-residential buildings, rental properties, and commercial facilities with fuel-burning equipment.

This guide covers everything Ontario building owners, property managers, landlords, and facility managers need to know about CO alarm requirements in 2026 — what the law requires, where alarms must be installed, who is responsible, what alarms must be replaced, and what happens when you don't comply.

What Laws Govern CO Alarms in Ontario?

Carbon monoxide alarm requirements in Ontario are governed by two overlapping frameworks:

The Ontario Fire Code (OFC) sets the requirements for CO alarms in existing buildings across Ontario. It has been amended several times over the past decade to expand coverage to more building types and occupancies.

The Ontario Building Code (OBC) sets requirements for CO alarms in new construction. Buildings built or significantly renovated after the OBC CO alarm provisions came into effect must meet the applicable OBC standards.

Together, these two codes cover virtually every occupied building in Ontario that contains a fuel-burning appliance, attached garage, or other CO hazard.

Where Are CO Alarms Required in Ontario?

Residential Buildings

CO alarms are mandatory in Ontario residential buildings where any of the following exist: a fuel-burning appliance (gas furnace, gas water heater, gas fireplace, wood-burning fireplace, oil furnace, etc.), an attached or built-in garage, or a storage garage located in the same building.

CO alarms must be installed adjacent to each sleeping area — meaning outside each bedroom or group of bedrooms on every floor that contains sleeping accommodations. If a fuel-burning appliance or fireplace is located on a floor without sleeping areas, an alarm is still required on that floor as well.

For multi-residential buildings, each dwelling unit that meets the above criteria must have CO alarms. Common areas with fuel-burning mechanical equipment may also require alarms. Condominium corporations are responsible for common area compliance; unit owners are responsible for their individual units.

Commercial and Institutional Buildings

Ontario's CO alarm requirements were expanded beyond residential to include commercial, industrial, and institutional occupancies where CO hazards exist. Buildings requiring CO alarms include:

• Buildings with fuel-burning appliances in occupied or adjacent spaces
• Commercial kitchens with gas cooking equipment
• Buildings with attached or integral parking garages
• Boiler rooms and mechanical rooms with gas or oil equipment
• Healthcare facilities, long-term care homes, and retirement homes
• Schools and hotels

What Type of CO Alarm Is Required?

All CO alarms installed in Ontario must be approved to CSA Standard 6.19. Under the Ontario Building Code, CO alarms in new construction must be interconnected — meaning when one sounds, all alarms sound simultaneously. This is not universally required in existing buildings under the OFC, but it is best practice.

How Long Do CO Alarms Last?

CO alarms have a finite lifespan — typically 5 to 7 years from the date of manufacture — after which the electrochemical sensor degrades and the alarm can no longer reliably detect carbon monoxide. The manufacture date is typically printed on the back or bottom of the unit. If your CO alarms are more than 7 years old from the manufacture date — not the installation date — they must be replaced.

Who Is Responsible for CO Alarm Compliance?

• Homeowners are responsible for their own installation, testing, and replacement.
• Landlords have a legal obligation to ensure CO alarms are installed and functional in all rental units — failure to comply can result in fire department orders and liability under the Residential Tenancies Act.
• Condominium corporations are responsible for common areas; unit owners for their own units.
• Commercial property owners are ultimately responsible regardless of tenant lease arrangements.

Testing and Maintenance Requirements

CO alarms should be tested monthly by pressing the test button. As part of your annual fire protection inspection, your certified technician should verify alarms are present in all required locations, bear the CSA 6.19 approval mark, and are within their manufacturer-specified lifespan. Establish a documented replacement schedule based on manufacture dates — particularly critical for property managers overseeing multiple units.

Combination Smoke and CO Alarms

Many Ontario buildings are now installing combination smoke/CO alarms approved to both ULC S531 (smoke) and CSA 6.19 (CO). These simplify compliance by reducing the number of devices to track and maintain.

What Happens If You Don't Comply?

• The local fire department can issue an Order to Comply.
• Under the Fire Protection and Prevention Act, fines reach up to $50,000 for individuals and $100,000 for corporations.
• Civil liability exposure is significant — Ontario courts have awarded substantial damages in CO poisoning cases involving landlord negligence.
• Property insurers increasingly review CO alarm compliance in claims investigations.

CO Alarm vs. Smoke Alarm — Key Differences

• Detects — Smoke Alarm: smoke particles. CO Alarm: carbon monoxide gas.
• Standard — Smoke Alarm: ULC S531. CO Alarm: CSA 6.19.
• Placement — Smoke Alarm: every floor, outside sleeping areas. CO Alarm: adjacent to sleeping areas and near CO hazards.
• Lifespan — Smoke Alarm: 10 years. CO Alarm: 5–7 years.
• Required in — Smoke Alarm: all residential buildings. CO Alarm: buildings with fuel-burning appliances or attached garages.

Both are required in most Ontario residential buildings. They are not interchangeable — one does not substitute for the other.

How First National Fire Protection Can Help

We provide CO alarm compliance assessments across Ontario including location audits, lifespan assessments, CSA verification, and integration with annual fire alarm and extinguisher inspections — one visit, full compliance picture.

📞 1-844-835-3473 | 📞 416-591-1393 | 🌐 firstnationalfire.com