Your Essential Guide to Carbon Monoxide Safety

Smoke crawling over smoke detector.

Carbon monoxide (CO) is a potentially deadly gas that is colourless, odourless and tasteless, hence its nickname, “the silent killer.” The gas is poisonous and can make you very sick; it can even lead to death. The good news is that carbon monoxide poisoning can easily be prevented with the installation of carbon monoxide alarms in all homes.

Sources of carbon monoxide

All fuel-burning equipment and appliances are potential sources of CO including: furnaces; chimneys; gas stoves; wood stoves; generators; gas-fueled water heaters; fireplaces; and car exhaust systems.

Symptoms in humans

Carbon monoxide enters the body through the lungs while breathing and “replaces” oxygen in the blood, preventing oxygen flow to the heart, brain and other vital organs. CO poisoning can be difficult to diagnose because its symptoms, including nausea, headaches, dizziness, fatigue, burning eyes and shortness of breath, are common to other illnesses. In more severe cases, people may also experience vomiting, confusion or unconsciousness.

Potential signs in the environment 

Here are a few things to look out for that could be signs of carbon monoxide in the home:

  1. A stale or stuffy feeling in the air
  2. Excessive moisture on windows or walls
  3. A sharp penetrating odour or smell of gas when the furnace or other fuel burning appliances are turned on
  4. Burning and pilot light flames are yellow/orange rather than blue
  5. The pilot light on the furnace or water heater goes out
  6. Chalky white powder or soot build-up occurs around the exhaust vent or chimney
  7. Damaged or discoloured bricks at the top of your chimney
  8. Moisture around the windows and walls near a furnace
  9. Excessive rust on vent pipes or the outside of appliances


Alarm placement do’s & don’t’s


  • Be sure your carbon monoxide alarm has been certified by the Canadian Standard Association (CSA).
  • Install CO alarms and smoke alarms on every floor of the home (including the basement) and near every sleeping area.*
  • Install a CO alarm near attached garages as cars produce CO when they are running.
  • If you use a combination smoke/CO alarm, install it near the ceiling (as per the manufacturer’s instructions) to ensure that it can detect smoke properly.


  • Place CO alarms in the following locations as it could damage the alarm or create a false alarm:
  • Close to fuel burning appliances
  • In excessively humid areas, like the bathroom
  • In direct sunlight
  • Near sources of blowing air, such as a vent, fan or open window
  • Near household cleaning products or paint thinners
  • Within 0.5 metres of cooking or open flame appliances such as stoves, fireplaces and furnaces
  • Close to automobile exhaust pipes

House demonstrating where to put CO and Smoke detector and fire extinguishers 


  • Clean CO alarms of dust and debris regularly.
  • Check or replace batteries at least twice a year and test the alarm monthly, or according to the manufacturer’s instructions.
  • CO alarms have a limited life (usually 7-10 years depending on the brand), so read the manufacturer’s instructions to see when to replace them.
  • Hire a professional each year to clean and check furnaces, gas-fired appliances, water heaters, and chimneys for leaks.
  • Make sure the fireplace damper is opened and cleared of debris before using.
  • Never use your oven, stove or gas or charcoal barbecue to heat your home.
  • Ensure fuel-burning equipment is vented to outside of the house and is kept clear and unblocked. Only use fuel-burning generators outdoors.
  • Make sure your clothes dryer’s exhaust duct is vented to the outside.
  • Clean out lint or debris regularly and check that the flapper moves freely.
  • Check the outside and inside walls of your house for cracks, holes, separations, and check for rust, stains or carbon deposits on heating ducts or pipes.
  • Never run your car (or any vehicle) inside your garage, even if the door is open.

What to do if your CO alarm goes off

If your CO alarm sounds, make sure that you and the occupants of your dwelling go outside immediately. If possible, open your windows and doors to ventilate your home before exiting. Getting to safety is a priority – then call 911.

A carbon monoxide alarm is the best way to protect you and your family from this potentially deadly threat. So take the time to learn about proper installation and maintenance to keep you and your loved ones safe.

* Sources for graphic: