Ontario CO Alarm Rules 2026: What Changed and What You Need

What the Old Rule Was

Before 2026, the Ontario Fire Code rule for CO alarms was simple: if your home had a fuel-burning appliance, a fireplace, or an attached garage, you needed one carbon monoxide alarm outside each sleeping area.[2] That meant a single alarm in the hallway outside the bedrooms covered most homes. Multi-storey houses with bedrooms on only one floor legally needed just one CO alarm.

That rule made some sense as a minimum, but it left big gaps. A gas furnace in a basement with no alarm in the basement could leak CO for hours before a second-floor alarm registered anything. An attached garage with no alarm in the adjacent room would not catch running vehicle exhaust until the gas had already drifted upstairs. The old rule was better than nothing, but it was not comprehensive.

What Changed on January 1, 2026

The province amended Ontario Regulation 87/25 under the Fire Protection and Prevention Act, effective January 1, 2026. The changes bring Ontario in line with the 2020 National Fire Code of Canada and tighten the CO alarm requirements in a specific way.[1]

The new rule, in plain language:[3]

1. Keep the old rule. You still need a CO alarm adjacent to each sleeping area. That part did not go away.
2. Add a CO alarm on every storey. This is the new part. If your home has a fuel-burning appliance, an attached garage, or a fireplace, every storey of the house needs its own CO alarm, including basements and floors that do not contain any bedrooms.

For a typical two-storey Ontario home with a basement and a gas furnace, that means:

• One CO alarm in the basement (where the furnace is)
• One CO alarm on the main floor (this can be the one adjacent to the sleeping area if bedrooms are on the main floor; if not, you need a separate main-floor alarm)
• One CO alarm on the upper floor outside the bedrooms

Three alarms. In a two-storey home with bedrooms only on the second floor, the old rule required one alarm. The new rule requires three.

Who the Rule Applies To

You are subject to the new rule if your home contains any of the following:[4]

• A fuel-burning appliance. Natural gas furnace, propane furnace, oil furnace, gas water heater, gas range, gas dryer, gas fireplace, wood stove, pellet stove, or any other device that burns fuel for heat or cooking.
• An attached garage. Any garage that shares a wall with the living space of the home, even if the door to the house is weather-stripped or the garage is not heated. Vehicle exhaust and fuel fumes can migrate inside.
• A fireplace. Wood-burning, gas, or pellet. Decorative-only electric fireplaces do not count.

The rule applies to all residential buildings: single-family detached, semi-detached, townhouse, and condominium.[2] Rental units and owner-occupied units are both covered. If you rent, the landlord is responsible for providing working alarms, but in practice both parties have obligations under the Residential Tenancies Act to maintain them.

If your home is fully electric (electric heat, electric cooking, no wood fireplace, no attached garage), the CO alarm rule technically does not apply to you. But if you share a wall with a neighbour who has any of those things (in a townhouse or semi-detached), buying a combo alarm is still smart. CO does not respect drywall.

Where Exactly the Alarms Go

The Fire Code specifies placement in general terms; the manufacturer's instructions fill in the details.[2] Here's the short version:

Adjacent to Each Sleeping Area

This is the hallway or corridor outside the bedrooms. Close enough that the alarm will wake someone sleeping with the bedroom door closed. In practice, this means the alarm goes in the hallway within a few metres of the bedroom doors. In a home with multiple sleeping areas on different floors, each cluster needs its own alarm.

Every Storey

Every storey of the house needs its own alarm. The basement counts. A finished attic or third storey counts. Each separate level of the home needs coverage.

The best placement per storey is usually:

• Basement: Near the top of the stairs leading up, or in the same room as the furnace (following the manufacturer's distance-from-vent guidance). Never inside a sealed utility closet where airflow is restricted.
• Main floor: In a central hallway or open area. If bedrooms are on the main floor, this alarm doubles as the sleeping-area alarm.
• Upper floors: In the hallway outside the bedrooms. Use this as your primary sleeping-area alarm.

Mount on the ceiling or high on a wall (CO is slightly lighter than air and mixes freely). Keep at least 3 metres from fuel-burning appliances to avoid false alarms from normal combustion byproducts. Do not install near vents, ceiling fans, or exterior doors where airflow dilutes readings.

Types of CO Alarms (and What to Buy)

The Fire Code allows three types of CO alarm. Each has trade-offs.[3]

For most homeowners, a sealed 10-year battery combination smoke and CO alarm is the simplest solution. You buy it, you mount it, you do not touch it for a decade, and when it chirps you replace it. No wiring, no outlets, no batteries to change at 2 am.

What to look for when buying:

• CSA, ULC, or ETL mark. This is the Canadian certification requirement. A UL mark alone is not enough; you need the Canadian equivalent.
• Sealed 10-year battery if you want fire-and-forget.
• Digital display for rooms where you want to see the actual CO level (useful near a furnace or garage wall).
• Manufacturer date within the last year. CO sensors degrade over time, even on the shelf. Check the date on the back of the package.

Skip voice-activated "smart" alarms that require Wi-Fi and a monthly subscription unless you specifically want the integration. They are more expensive and add failure modes (router down, subscription expired) that a basic alarm does not have.

Replacing Old Alarms

CO alarms do not last forever. The sensor chemistry degrades whether or not the alarm has been triggered. Most CO alarms have a 7 to 10 year lifespan from the manufacturing date printed on the back (not from when you bought it). After that, the alarm may still beep to indicate end of life, but it may also silently fail and just stop detecting anything.

The quick audit you can do in 15 minutes:

1. Walk the house and list every CO alarm you find.
2. Count the storeys of the home. You should have at least one alarm per storey (if your home has the triggers), plus one adjacent to each sleeping area.
3. Take down each existing alarm and check the manufacture date on the back. If it's older than 7 years (check the specific alarm's expiry, some are 10), replace it.
4. Press the test button on each alarm. If it does not beep loudly, replace the battery (if applicable) or the entire unit.
5. If you're short on coverage, buy what you need at a hardware store. Big box stores stock plenty of CSA/ULC certified units.

For a typical three-storey home (basement + main + upper), full compliance is usually three alarms. At $50 each for good combo units, that is $150. For most families this is one of the cheapest pieces of home safety you will ever buy.

Enforcement and Why It Matters Beyond Fines

The Ontario Fire Code is enforced through local fire services under the Fire Protection and Prevention Act.[1] Fines for non-compliance with CO alarm rules start around a few hundred dollars and scale up based on circumstances (a fine after a CO incident is higher than one during a routine inspection). But the fine is the least of the real consequences.

• Insurance claim denial. Home insurance policies generally require you to comply with applicable safety regulations. If a CO leak causes injury, hospital bills, or a fire-related loss, the insurer will check whether the house was compliant. Missing alarms can lead to reduced payouts or outright denial of claims.
• Criminal liability. If someone in the home is hurt or killed by CO poisoning in a house that did not have legally required alarms, the homeowner or landlord can face criminal negligence charges. This is rare but it happens, and it is always worse for the landlord who ignored the law than for the homeowner who did not know about it.
• Real estate closing problems. Buyers' home inspectors check for CO alarms as a standard line item. Missing alarms do not usually kill a deal, but they will be noted in the inspection report and can be a negotiating lever for the buyer.
• Rental unit inspections. If you own a rental, municipal property standards or fire services can inspect on complaint and order compliance within a set period. Repeat non-compliance leads to fines and, in extreme cases, orders forcing the tenant to vacate until the issue is resolved.

The Silent Killer Math

CO is called the silent killer because you cannot see it, smell it, or taste it.[2] A leaking furnace or blocked vent can fill a house with CO over hours while the people inside gradually get headaches, confusion, and eventually pass out. Low-level chronic exposure causes subtler problems: persistent headaches, fatigue, nausea that goes away when you leave the house. If you have any of those symptoms and a fuel-burning appliance, check your alarms and get the appliance inspected.

The leading causes of home CO incidents in Ontario are malfunctioning furnaces, blocked furnace vents (often from ice or snow drifts), cars running in attached garages, and improperly installed gas appliances. All of these are catchable by a working CO alarm in the right location.

A $50 alarm detects any of them within minutes and gives everyone in the house time to get out and open the windows. The people who die from CO poisoning are almost always the ones who either had no alarm or had an expired one that silently failed. Do not be either of those people. Fixing this is embarrassingly cheap and takes less than an hour.

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