In Ontario, over 65% of carbon monoxide deaths and injuries occur in homes. Most people have heard of carbon monoxide and know that it's dangerous. However, it's often a mystery of where it comes from, how it's produced and what precautions can be taken to ensure it doesn't endanger you or your family.

What is Carbon Monoxide?

Carbon Monoxide (CO) is a colourless, odourless, tasteless and toxic gas and is often referred to as the "silent killer". Carbon monoxide poisoning is a leading cause of accidental poisoning deaths in North America.

Exposure to CO can cause flu-like symptoms such as headaches, nausea, dizziness, burning eyes, confusion, drowsiness and even loss of consciousness, without the elevated temperature associated with the flu. In severe cases, CO poisoning can cause brain damage and death. The elderly, children and people with heart or respiratory conditions may be particularly sensitive to CO.

How is CO produced?

Carbon monoxide is commonly produced as a by-product of combustion when common fuel-burning appliances and equipment that use natural gas, oil, wood, propane and kerosene, don't get enough air to burn up completely. When this happens, carbon monoxide can build up, especially in a confined room or space. This can lead to toxic effects on humans and pets. 

What are the sources of CO in my home? 

Home Diagram - Common Sources of Carbon MonoxideMost households have on average 4-6 appliances that produce carbon monoxide.

  1. Furnace
  2. Water Heater
  3. Dryer
  4. Fireplace
  5. Stove
  6. Car
  7. BBQ
  8. Blocked Vents or Chimney

View the diagram - Common Sources of Carbon Monoxide

How to prevent the build-up of CO in your home:

  • Ensure fuel-burning appliances, chimneys and vents are cleaned and inspected by professionals every year before cold weather sets in. Visit to find a registered contractor near you.
  • Ensure vents for the dryer, furnace, stove, fireplace and other fuel-burning appliances should always be clear of snow and other debris.
  • Gas and charcoal barbeques should only be used outside, away from all doors, windows, vents, and other building openings. Never use barbeques inside garages, even if the garage doors are open.
  • Portable fuel-burning generators should only be used outdoors in well-ventilated areas away from windows, doors, vents and other building openings.
  • Ensure all portable fuel-burning heaters are vented properly, according to manufacturer's instructions.
  • Never use the stove or oven to heat your home.
  • Open the flue before using a fireplace for adequate ventilation.
  • Never run a vehicle or other fueled engine or motor inside a garage, even if the garage doors are open. Always remove a vehicle from the garage immediately after starting it.

Install Carbon Monoxide Alarms, it's the law!

A properly installed and maintained CO alarm can alert you to when the poisonous gas is present. They usually have a life expectancy of approximately 5-7 years or as indicated by the manufactures requirements.

If the alarm sounds, evacuate your home quickly. Call the fire department from outside and ask them to check your home for the presence of carbon monoxide.

Single Family Dwellings

  • House Diagram - Alarm Location GuidelinesIf your home has a fuel-burning appliance or an attached garage, install a CO alarm adjacent to each sleeping area.
  • For optimum protection, it is recommended that additional CO alarms be installed in other levels and/or areas of the home that are in proximity to a CO source, subject to the distance limits provided in the product's instruction manual.

View the diagram - Alarm Location Guidelines

Apartment and Condominium Buildings

  • If there is a fuel-burning appliance in your condo/apartment, install a CO alarm adjacent to each sleeping area.
  • If your building has a service room, CO alarms must be installed in the service room and adjacent to each sleeping area of all condos/apartments above, below and beside the service room.
  • If your building has a garage, CO alarms must be installed adjacent to each sleeping area of all condos/apartments above, below and beside the garage.

In rental properties the landlord is responsible for the installation and maintenance of CO alarms. The landlord is also responsible for providing the tenant with CO alarm maintenance instructions. Tenants are responsible for notifying the landlord as soon as they become aware that a CO alarm in their unit is disconnected, not operating, or its operation is impaired. Also, tenants shall not disable their CO alarms.

In condominiums, the owner of the suite is responsible for the installation and maintenance of CO alarms in the suite. Often, there are agreements between the owner and the condominium corporation in which the corporation takes on this responsibility on behalf of the owner. In a situation where the condominium owner rents out the suite to a tenant, the owner takes on the role of the landlord and is responsible for the installation and maintenance of the CO alarms.

Help prevent carbon monoxide from harming you and your family by:

  1. Getting an annual inspection for all fuel-fired appliances in your home
  2. Installing and regularly testing carbon monoxide alarms

For more information on carbon monoxide, visit TSSA or the Office of the Fire Marshal.