Carbon Monoxide Poisoning Prevention: Protecting Your Family This Winter
Carbon monoxide is colourless and odourless — and a working CO alarm is your family’s first line of defence. Here is how to prevent poisoning and what to do if your alarm sounds.
Carbon monoxide (CO) is a colourless, odourless gas you cannot detect without an alarm. Prevent poisoning by installing a working CO alarm on every level of your home and outside sleeping areas, servicing fuel-burning appliances yearly, and never running a generator, BBQ, or vehicle in an enclosed space. If your alarm sounds or anyone has flu-like symptoms without a fever: get everyone (and pets) outside into fresh air, call 911, and do not re-enter until responders say it is safe. Poison Control (1-844-POISON-X) can also advise on symptoms.
Carbon monoxide (CO) is produced by the incomplete combustion of fuels — natural gas, propane, oil, wood, charcoal, and gasoline. You cannot see it, smell it, or taste it. When inhaled, it replaces oxygen in the bloodstream, starving the brain, heart, and other organs. At high concentrations, it can kill within minutes.
Winter is peak season for carbon monoxide poisoning because furnaces, fireplaces, space heaters, and generators are running — often in tightly sealed homes. Children, elderly people, and pregnant women are especially vulnerable because they are affected by lower concentrations faster.
Sources of Carbon Monoxide in Your Home
- Furnaces — cracked heat exchangers, blocked vents, or malfunctioning burners
- Water heaters — gas-powered water heaters in poorly ventilated spaces
- Fireplaces and wood stoves — blocked chimneys, closed dampers, or creosote buildup
- Attached garages — running a vehicle in a closed or partially closed garage, even briefly
- Portable generators — must never be operated indoors, in a garage, or near open windows
- Gas stoves and ovens — using a gas oven for heating is a common and dangerous practice
- BBQs and charcoal grills — never use indoors or in enclosed spaces, even partially enclosed ones like a tent or screened porch
CO Detector Placement and Maintenance
- Install a CO alarm on every level of your home, including the basement
- Place alarms outside each sleeping area — CO poisoning often occurs while the family is asleep
- Follow manufacturer instructions for mounting height — some are designed for wall mounting, others for ceiling
- Test alarms monthly by pressing the test button
- Replace batteries annually (or when the low-battery warning sounds)
- Replace the entire alarm unit by the replacement date printed on the manufacturer’s label — most units are certified for a lifespan of roughly 5 to 10 years, but the exact figure varies by model
- Do not install CO alarms directly above or beside fuel-burning appliances — this can cause false alarms
Alarm placement and replacement follow the manufacturer’s certification label and Ontario fire-code / Hawkins Gignac Act requirements; confirm the exact replacement date on the back of your unit.
Recognising CO Poisoning Symptoms
CO poisoning symptoms are often mistaken for the flu — which is particularly dangerous in winter when flu is common. The key difference: CO poisoning does not cause a fever.
| Mild Exposure | Moderate Exposure | Severe Exposure |
|---|---|---|
| Headache | Severe headache | Confusion, disorientation |
| Dizziness | Drowsiness, lethargy | Loss of consciousness |
| Nausea | Vomiting | Seizures |
| Fatigue | Confusion | Cardiac arrhythmia |
| Shortness of breath on exertion | Rapid heart rate | Death |
Source: Canadian Red Cross first aid guidance on poisoning and inhaled toxins; symptom progression per Poison Control Canada. Any altered level of responsiveness or difficulty breathing means call 911, not just Poison Control.
What to Do If Your CO Alarm Sounds
- Do not ignore it — do not assume it is a false alarm or a low battery
- Get everyone out of the house immediately — including pets — and into fresh air
- Call 911 from outside. If anyone has symptoms, you can also call Poison Control at 1-844-POISON-X (1-844-764-7662) for guidance
- Do not re-enter until emergency services have declared it safe
- If anyone has symptoms, tell the paramedics — they may provide oxygen and hospital evaluation
Source: Canadian Red Cross poisoning first aid — for any inhaled poison, move the person to fresh air and call EMS; Poison Control Canada (1-844-POISON-X) directs symptom management. Move to fresh air only if it is safe for you to do so.
Prevention Checklist for Winter
Annual maintenance
- Have your furnace, water heater, and any fuel-burning appliances inspected annually by a qualified technician
- Have your chimney and flue inspected and cleaned before the first fire of the season
- Check that all exhaust vents (furnace, dryer, water heater) are clear and unblocked — snowdrifts can cover exterior vents
- Test all CO alarms and replace batteries
- Check CO alarm expiry dates — replace units past the replacement date on the manufacturer’s label
Ongoing safety rules
- Never run a vehicle in an attached garage, even with the door open
- Never use a portable generator indoors or in a garage
- Never use a gas oven or stovetop to heat your home
- Never use a BBQ, charcoal grill, or camp stove indoors
- After a heavy snowfall, check that exterior vents are not blocked by snow or ice
Frequently Asked Questions
How many CO detectors do I need?
Ontario law requires a CO alarm on every level of your home if you have a fuel-burning appliance or an attached garage. At minimum, install one on each storey and outside sleeping areas. For maximum protection, also place one near your furnace room, attached garage entry, and any room with a fuel-burning appliance, following the manufacturer’s spacing guidelines.
What are the symptoms of carbon monoxide poisoning?
Early symptoms include headache, dizziness, nausea, fatigue, and shortness of breath — often mistaken for the flu. Unlike the flu, CO poisoning does not cause a fever. As exposure increases, symptoms progress to severe headache, confusion, vomiting, rapid heart rate, and loss of consciousness. If multiple family members develop similar symptoms simultaneously, especially in winter, suspect CO poisoning and get everyone outside immediately.
Can CO poisoning happen in summer?
Yes. While most cases occur in winter due to heating appliance use, CO poisoning can happen year-round. Summer risks include portable generators (especially during power outages), running vehicles in attached garages, BBQs or camp stoves used in enclosed spaces, and gas-powered tools or equipment used in poorly ventilated areas.
How often should I replace my CO detector?
Follow the replacement date printed on the manufacturer’s label on the back of your alarm — most CO alarms are certified for a lifespan of roughly 5 to 10 years, but the exact figure varies by model. Replace the unit when it reaches that date, even if it appears to be working, because the sensor degrades over time. Replace batteries annually or when the low-battery warning sounds, and test the alarm monthly.
What should I do if my CO alarm goes off?
Get everyone out of the house immediately, including pets. Do not try to find the source. Call 911 from outside. Do not re-enter the house until emergency services have declared it safe. If anyone has symptoms of CO poisoning (headache, dizziness, nausea, confusion), tell the paramedics — they may need oxygen therapy or hospital evaluation. You can also call Poison Control (1-844-POISON-X) for guidance. Never assume a CO alarm is malfunctioning.
Sources & medical review
Reviewed by Milos Radojcic (Canadian Red Cross / Heart & Stroke / Lifesaving Society First Aid & CPR Instructor, 10+ yrs). Clinical content aligned with Canadian Red Cross poisoning first aid, the Heart & Stroke Foundation of Canada, and the 2025 ILCOR consensus; poisoning direction per Poison Control Canada (1-844-POISON-X); CO-alarm and fuel-safety requirements per Ontario’s Hawkins Gignac Act and applicable fire codes. CO-alarm lifespan figures should be confirmed against your unit’s certification label. Last reviewed July 2026.