Carbon monoxide (CO) is a colourless, odourless gas that can be deadly. You can’t see it, smell it, or taste it – it is only detectable by a working CO alarm.
CO is created when fuels like propane, natural gas, heating oil, or wood don’t burn completely in appliances such as furnaces, fireplaces, water heaters, stoves, or BBQs. More than 65% of CO-related injuries and deaths in Ontario happen at home.
New Requirements
Since 2014, Ontario law has required CO alarms outside all sleeping areas in homes with fuel-burning appliances, fireplaces, or attached garages. As of January 1, 2026, the rules have expanded to give residents even more protection.
If your home has a fuel-burning appliance, fireplace, attached garage, or receives heated air from a fuel-burning appliance outside the home (like in a utility shed), you must install CO alarms:
- On every storey of your home
- On storeys with bedrooms, the alarm must be located in the hallway outside the bedroom
These rules also apply to multi-unit buildings and homes where residents need extra help during emergencies.
Choosing an Alarm
CO alarms can be hardwired, battery-operated, or plug-in. Many models combine smoke and CO detection in one unit (“combo unit”).
When purchasing an alarm, look for one that meets Canadian safety standards. Check for logos from recognized agencies like:
- CSA (Canadian Standards Association)
- ULC (Underwriters Laboratories of Canada)
- ETL (Electrical Testing Laboratories)
Maintenance Tips
Like smoke alarms, CO and combo alarms need simple maintenance to make sure they are working correctly.
- Test alarms every month using the test button.
- Replace batteries every year (or as needed).
- Replace alarms according to the manufacturer’s instructions and expiry date.
If your alarm chirps, it could mean a low battery or that the alarm has reached its end of life. Make sure you check the manufacturer’s guide to know the difference between a low-battery warning, end-of-life signal, and an emergency alarm.
Please see below for more information about CO alarms, or to request an alarm for your home.
- Smoke & Carbon Monoxide Alarm FAQs
- What are combo units?
Combo units are combination alarms that detect more than one hazard in a single device. The most common combo unit is a smoke alarm and CO alarm in one housing.
- Why use a combo unit?
Combo units are popular because they:
- Save space (one device instead of two)
- Reduce installation time
- Cost less than buying separate alarms
- Provide simpler maintenance (fewer devices to manage)
- How often do combo units need to be replaced?
Most combo units need to be replaced every 7–10 years, depending on the manufacturer.
Typical guidelines:
- Smoke sensor: about 10 years
- CO sensor: about 5–10 years
Because both sensors are in one unit, you replace the entire combo unit when either sensor reaches end-of-life.
Always:
- Test your alarms monthly and replace the batteries immediately when required.
- Check the manufacture date on the back.
- Read and follow the manufacturer’s replacement instructions.
- Where can I purchase carbon monoxide, smoke or combo alarm units?
All these units can be purchased at your local hardware store. It is essential for your safety to ensure that any unit purchased is approved and properly certified for use in Canada and includes a Canadian certification mark.
For information on what to look for when purchasing smoke and carbon monoxide alarms, see the Certification Marks listed on the Government of Canada's Fire Safety page.
Middlesex Centre residents can request a free combo alarm. Please see below for details.
- Do carbon monoxide (CO) alarms need to be low to the ground?
No. Carbon monoxide is about the same weight and buoyancy as air, so it mixes evenly throughout a room. Because of this, CO alarms do not need to be placed low to the ground.
For the best placement, follow the manufacturer’s recommendations:
- On a wall at about eye level
- On the ceiling
- Outside sleeping areas and on every level of the home
Avoid placing them:
- Right next to fuel-burning appliances
- In kitchens or bathrooms (humidity can cause false alarms)
- What should I do if my alarm sounds?
Common signs of CO exposure include headache, dizziness, nausea, confusion, weakness, and shortness of breath. In severe cases, CO poisoning can cause loss of consciousness.
If your CO alarm sounds or you notice these symptoms you should leave your home immediately, get fresh air, and call 911 from outside.
- Request a Combo CO/Smoke Alarm
Thanks to a generous donation from Enbridge Gas, Middlesex Centre Fire Services is offering CO/Smoke Alarms for Middlesex Centre residents (one per household, as supply lasts). Please complete our online form to request one today.
- For More Information
Visit:
- Middlesex Centre Fire Services - Fire Prevention & Safety
- Government of Ontario - Carbon Monoxide Safety
- Government of Canada - Fire Safety in your Home
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