Ontario's carbon monoxide alarm rules, written for the person installing them

Last updated: September 2026

Quick answer

• Existing buildings: Ontario Fire Code, O. Reg. 213/07, Division B, Section 2.16. New construction: Ontario Building Code, Division B, Subsection 6.9.3.
• Same trigger in both: a residential or care occupancy with a fuel burning appliance, a fireplace or flue, a storage garage, or heat from a forced air fuel burning appliance located elsewhere.
• Since 1 January 2026, O. Reg. 87/25 added the every storey rule. Adjacent to each sleeping area is no longer enough on its own.
• In multi unit buildings, alarms go in the service room, adjacent to sleeping areas in suites sharing a wall, floor or ceiling with that room or a storage garage, and in directly heated public corridors at not more than 25 m spacing.
• The alarm standards are CSA 6.19 and UL 2034, and only those two. CAN/ULC-S531 is the smoke alarm standard and has nothing to do with CO.
• A CO detector wired to a fire alarm panel is a different device, listed to CAN/ULC-S588 (currently CAN-ULC-588-2024A). Ontario does not require it and does not say what signal it must produce.
• Power in existing buildings can be hardwired, plug in or battery. New construction must be hardwired with no disconnect, battery backup and interconnection within the suite.

Which code applies to the building in front of you

The Ontario Fire Code (O. Reg. 213/07) applies to buildings in operation, it is retroactive, and it is the document a fire inspector works from. CO alarm installation is Division B, Section 2.16; maintenance and testing is Division B, Subsection 6.3.4. The wider picture on that split is in building code versus fire code in Ontario.

The Ontario Building Code applies at the time of construction or a permit. Its CO requirements are in Division B, Subsection 6.9.3: 6.9.3.1 application, 6.9.3.2 suites, 6.9.3.3 service rooms outside suites, 6.9.3.4 installation and standards. They are tighter than the Fire Code ones.

Article 2.16.1.1 also exempts buildings where the alarms were already installed to Building Code requirements. Sentence (2) puts the cut off at 1 January 2025: the Section does not apply where carbon monoxide alarms were installed in accordance with the Building Code as it read at any time on or after that date. Confirmed 5 September 2026 against the official e-Laws consolidation of O. Reg. 213/07, consolidation period beginning 1 January 2026.

Where the Fire Code puts them

Article 2.16.2.1 splits the requirement four ways. Read it as four separate installations.

The every storey and public corridor language are the January 2026 additions made by O. Reg. 87/25. TSSA confirms the date and points at Section 2.16 of Division B as the amended provision. Before that, an alarm outside the bedrooms was the whole requirement in a house, which is why most municipal pages still describe the older rule.

Note what is not in there. The Fire Code does not require alarms in suites that merely sit across a corridor from a service room, or in every suite just because the building has a boiler room. The trigger is the shared assembly.

What "adjacent to each sleeping area" actually means

Neither code gives you a dimension. There is no equivalent of the audibility numbers you get for a fire alarm system. You get a performance test instead: the alarm has to be audible in the sleeping rooms with the intervening doors closed. Fire Code Sentence 2.16.2.1.(8) and Building Code Clause 6.9.3.4.(1)(d) both say a version of this.

In a typical house, one alarm in the bedroom hallway satisfies it. In a bungalow with bedrooms split by a living room, one in the middle probably does not, so put one outside each cluster. If the AHJ wants a second device, that is a cheap argument to lose.

Where the alarms must not go

Neither code gives you a prohibited locations list. Both defer to the manufacturer's instructions, which is why Article 6.9.3.4 sets the mounting height by the manufacturer's recommendation and only falls back to on or near the ceiling when the instructions are silent. Follow the sheet in the box and keep it with the file.

For the practical list, the Ontario Association of Fire Chiefs publishes the placements that stop an alarm working: below 4.4 C or above 37.8 C, exposed to chemical fumes, within 1.5 m of any cooking or open flame appliance, or in an exhaust stream. That is fire service guidance, not a code clause, but it is why a device nuisance trips over a stove or dies in an unheated garage.

What the Building Code adds in new construction

Article 6.9.3.2 goes further than the Fire Code in two places. Sentence (4) puts an alarm inside the sleeping room itself where that room contains a fuel burning appliance or flue, or shares a wall, floor or ceiling assembly with a storage garage or with a room outside the suite containing an appliance or flue. That is the one people miss on a bedroom above a parking garage. Sentence (3) handles bachelor suites: where the suite is a combined living and sleeping area, the alarm goes in that combined area.

Article 6.9.3.3 covers the rest of the building: a CO alarm is required in a service room or other area containing a fuel burning appliance used for building services or laundry drying equipment, where that area is not inside a suite of residential occupancy. That catches the dryer room and the make up air unit.

Power and interconnection

This decides whether you are pulling a circuit.

Fire Code, Sentence 2.16.2.1.(5). In an existing building the alarm may be permanently connected with no disconnect switch between the overcurrent device and the alarm, or battery operated, or plugged into a receptacle. All three are legal, and there is no interconnection requirement. An owner retrofitting a 1968 house can hang three battery units and be compliant.

Building Code, Sentence 6.9.3.4.(1). In new construction the alarm shall be permanently connected with no disconnect switch between the overcurrent device and the alarm, shall have battery backup good for not less than 8 h in standby followed by 12 h of alarm signal, and shall be interconnected so that one alarm activating in a suite activates all the alarms in that suite. Corridor alarms interconnect across the corridor the same way.

The wiring rules live in Rule 32-110 of the Canadian Electrical Code, adopted in Ontario as the Ontario Electrical Safety Code, which covers permanently connected smoke alarms and CO alarms in dwelling units together. A Canadian trade guide to Section 32 sets out what you would expect: a circuit whose loss would be noticed, no disconnect between the alarm and the branch circuit overcurrent device, no GFCI or AFCI in that path, and Class 2 permitted for interconnection. That is a secondary source, not the code book, so verify it in the edition your jurisdiction has adopted. More in CEC Section 32 for fire alarm circuits.

Standalone CO alarm or CO detector on the fire alarm system

Two different devices, two standards, two jobs. Confusing them is the most common error on a commercial submittal.

It is the same split as smoke alarm versus smoke detector: the alarm is a complete appliance, the detector is an initiating device on somebody else's system. See the CO detector entry.

Two corrections, because these designations get mangled constantly. CAN/ULC-S531 is the Standard for Smoke Alarms, the 2014 edition withdrawn and superseded by CAN/ULC-S531:2019. It has nothing to do with carbon monoxide. And CAN/ULC-S588 is not a carbon monoxide standard by title. It is the gas and vapour detector and sensor standard, currently CAN-ULC-588-2024A, SCC approved 22 August 2024, and its scope explicitly excludes fire alarm control units and residential CO alarms. It is still what the ULC listed addressable CO detectors sold in Canada carry: a major manufacturer's Canadian product page for its addressable CO detector states CAN/ULC-S588 alongside the American UL 2075.

When CO detection is tied into the fire alarm system

Neither the Ontario Building Code nor the Ontario Fire Code requires CO detection to be connected to a fire alarm system, and neither tells you what signal it should produce. The code requirement is satisfied by listed CO alarms. When you find CO detectors on a fire alarm control unit in Ontario, it is because the specification asked for it, or the owner wanted the annunciator and the monitoring station to see it.

That makes the signal type a design decision recorded in the specification and the fire alarm matrix, not a code fact. In practice CO points on a Canadian panel are configured as supervisory or ancillary rather than fire alarm, because the right response to CO is to ventilate and leave by the normal route, not to push everyone into a stairwell that may be the contaminated space. For the vocabulary, read alarm, supervisory and trouble signals.

What we could not verify: whether CAN/ULC-S524 or CAN/ULC-S527 mandates a classification for a CO input, and what the annunciator must display. Both are copyrighted and paywalled and we will not paraphrase a clause we have not read. Do not take the American answer either: NFPA 72 has a distinctive CO audible signal and a whole chapter on CO detection, and none of it is a requirement here. If the drawings call for CO on the panel, get the signal type, annunciation and matrix behaviour written into the specification and confirmed by the engineer of record before you commission. There is no code default to fall back on.

The parking garage system that is not a fire alarm system

Technicians get called to this one and then find it is not their scope. Ontario Building Code Article 6.2.2.3 requires storage garage ventilation to be controlled automatically by carbon monoxide monitoring devices where gasoline powered vehicles are used, or nitrogen dioxide devices for diesel, holding 100 ppm CO and 3 ppm NO2, with tighter numbers in repair garages. That is a mechanical control system on a ventilation contract, not a fire alarm system. It is not covered by CAN/ULC-S537 verification, and its sensors are not the suite CO alarms required by Subsection 6.9.3.

Testing, replacement and the owner's obligations

Fire Code Subsection 6.3.4 is short, and it is the part building owners lose prosecutions over.

• 6.3.4.3 CO alarms and their power supplies maintained in operating condition.
• 6.3.4.4 landlord gives the tenant the manufacturer's maintenance instructions or approved alternatives.
• 6.3.4.5 tenant tells the landlord when an alarm is disconnected, not operating or impaired.
• 6.3.4.6 no person shall disable a carbon monoxide alarm.
• 6.3.4.7 replacement within the manufacturer's stated timeline, conforming to CSA 6.19 or UL 2034.
• 6.3.4.8 landlord tests annually, on a change of tenancy, and after any battery change or electrical work affecting the alarm.

Note what 6.3.4.7 does not do: it gives you no number. The code defers to the end of life date on the unit. That is 7 to 10 years for most current sealed units and shorter for older stock, and the Ontario Association of Fire Chiefs still describes many alarms as expiring at five to seven years. Read the label. There is also no CAN/ULC maintenance standard for CO alarms the way Fire Code Article 6.3.2.6 points interconnected smoke alarms at CAN/ULC-S552.

The exposure under the Fire Protection and Prevention Act is real: the City of Toronto publishes the penalties as up to $50,000 and one year in jail for an individual, and up to $500,000 for a corporation. More in the guide for building owners.

How the rules got here

Ontario's retroactive requirement arrived with the Hawkins-Gignac Act, in force 15 October 2014, phased in: six or fewer residential suites by 15 April 2015, more than six suites by 15 October 2015, maintenance and testing duties immediately. That structure is set out in the Office of the Fire Marshal amendment guidance municipalities reproduce. O. Reg. 87/25 is the second wave, effective 1 January 2026, and we found no phase in this time.

What an inspector actually checks

• One alarm adjacent to each sleeping area, and one on each storey without a sleeping area.
• The service room alarm, and the alarms in suites sharing an assembly with that room or the storage garage.
• Corridor alarms where the corridor is directly heated, and the spacing between them.
• The label: CSA 6.19 or UL 2034, and the manufacturer's expiry date.
• Whether it is still powered, still mounted, and not painted over or bagged.
• In a rental, whether the tenant got the instructions and whether the annual test is logged.

Nobody will ask you for a certificate of verification on CO alarms, because there is no CAN/ULC-S537 requirement attached to them. If CO detectors are on the fire alarm system, they are part of that system's verification and annual inspection, covered in verification versus annual inspection.

How other provinces differ

British Columbia is the useful contrast. The BC Building Code's CO provisions, published free on BC Publications, permit a carbon monoxide detection system installed to CAN/ULC-S524 as an alternative to CO alarms in some occupancies. Ontario's Subsection 6.9.3 has no equivalent permission in the articles we read, so that is the clause that will not travel if you carry a BC specification east. See fire alarm in British Columbia and fire alarm in Alberta.

The injury prevention charity Parachute's national summary puts Alberta, Manitoba, Quebec, Saskatchewan and Yukon in the direct legislation group, and BC, New Brunswick, Nova Scotia, PEI and Newfoundland and Labrador in the group working from the National Building Code. Ontario's retroactive duty on existing buildings is not universal, so do not assume it.

What to confirm before you quote a job

• The official text. Section 2.16 and Subsection 6.3.4 of Division B were confirmed against the official consolidation on Ontario e-Laws, consolidation period beginning 1 January 2026, e-Laws currency date 2 September 2026, last amendment O. Reg. 303/25. The every storey rule is in Clauses 2.16.2.1.(1)(b), (2)(c) and (3)(b), the public corridor rule is in Clause 2.16.2.1.(4)(b), and the 25 m corridor spacing is in Subclause 2.16.2.1.(4)(b)(ii). Sentence 2.16.1.1.(2) exempts a building where carbon monoxide alarms were installed in accordance with the Building Code as it read at any time on or after 1 January 2025. Read it at e-Laws.
• The Building Code exemption date in Article 2.16.1.1. The 1 January 2025 cut off is unconfirmed.
• The signal classification for CO on a fire alarm panel. Not a code fact in Ontario. Get it in the specification.
• Whether your AHJ reads "adjacent" the way you do. There is no dimension in the code.
• The current edition of anything. This page was researched in September 2026 and requirements change.

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