Key Takeaways
- Affected Ontario homes now require CO alarms on every storey and adjacent to sleeping areas.
- Carbon monoxide cannot be seen, smelled, or tasted, making working alarms essential.
- Test alarms monthly, replace them as directed, and treat every CO alarm as an emergency.
As of January 1, 2026, Ontario’s carbon monoxide alarm requirements have expanded. Affected homes must now have alarms on every storey, as well as adjacent to sleeping areas.
Carbon monoxide (CO) has no colour, smell, or taste, so a working alarm may provide the first warning that it is present. Checking your home’s alarm coverage now can help protect your household and ensure your home meets the updated requirements.
Which Ontario Homes Need CO Alarms?
The requirements apply to homes with:
- A fuel-burning appliance, such as a gas furnace or water heater
- A fireplace
- An attached garage
- Heating supplied by a fuel-burning appliance outside the home, such as one in a utility shed
In rental properties, landlords are responsible for installing, maintaining, and completing required tests of CO alarms. Tenants must report malfunctioning alarms and must not remove batteries or disable the devices.
For more information about affected homes and resident responsibilities, review Ontario’s official carbon monoxide safety guidance.
Where Should CO Alarms Be Installed? Carbon Monoxide Placement
Begin by identifying every storey and sleeping area in the home. For example, a two-storey house with bedrooms upstairs and a basement may require one alarm in the hallway near the bedrooms, another on the main floor, and another in the basement.
Always follow the manufacturer’s instructions for mounting height and the appropriate distance from fuel-burning appliances, vents, windows, bathrooms, and other locations that could interfere with the alarm.
For split-level homes, open-concept layouts, or unusual heating arrangements, consult Ontario’s official guidance or contact the local fire department.
Common Sources of Carbon Monoxide at Home
Carbon monoxide can build up when fuels such as natural gas, propane, oil, gasoline or wood do not burn completely, or when combustion gases are not properly vented outside.
It’s important to understand that CO build up and natural gas leak are different safety concerns. Natural gas is odourless on its own, so utilities add a sulphur-like, rotten-egg smell to help you detect leaks. Carbon monoxide has no colour, smell or taste. A CO alarm detects carbon monoxide, but it will not detect a natural gas leak.
If you smell natural gas, leave the home immediately without using light switches, electronics or phones inside. Call your gas utility’s emergency line or 911 once you are safely outside.
Common sources of CO include:
- Furnaces, boilers, and fuel-burning water heaters
- Gas or wood-burning fireplaces
- Gas stoves and ovens
- Blocked or damaged chimneys and exhaust vents
- Vehicles running in attached garages
- Generators, grills, and fuel-powered tools used in enclosed spaces
Never use outdoor cooking or heating equipment inside your home. Always operate generators and other fuel-powered equipment outdoors and away from windows, doors and vents.
What Should You Do If a CO Alarm Sounds?
Treat every CO alarm as an emergency:
- Get everyone — including pets — outside immediately.
- Call 911 or the fire department.
- Seek medical attention as directed by emergency responders.
- Do not re-enter until emergency personnel say it is safe.
- Have suspected equipment inspected before using it again.
Possible exposure symptoms include headache, dizziness, nausea, weakness, confusion, chest pain, and shortness of breath. Do not remain inside to find the source, open windows, or silence the alarm.
Check out our tips for preventing CO poisoning.
Maintain Your CO Alarm and Reduce Risk
Include these steps in your household safety routine:
- Test every CO alarm monthly.
- Replace batteries when directed or when a low-battery warning sounds.
- Check each alarm’s replacement date and replace expired units.
- Keep alarms clean, uncovered, and free from paint.
- Have fuel-burning equipment and venting serviced as recommended.
- Keep outdoor exhaust outlets clear of snow, ice, leaves, and debris.
- Never run vehicles, generators, or cooking grills in enclosed spaces.
- Use patio heaters outdoors only.
Professional maintenance can identify certain equipment or venting problems, but it cannot replace functioning CO alarms. Required alarms should remain installed regardless of how recently heating equipment was serviced.
A periodic chirp may indicate a low battery, fault, or expired alarm. Consult the manufacturer’s instructions, but never assume a full alarm signal is only a device problem.
Check Your Home’s CO Alarm Coverage
Ontario’s updated CO alarm rules are an important reminder that carbon monoxide safety starts with working alarms in the right places. By checking every storey and sleeping area, testing alarms regularly, and replacing expired units, residents can help protect everyone in the home.
CO alarms work alongside responsible equipment use and regular maintenance — not in place of them. Taking these simple precautions can help Ontario households stay safer and better prepared.