Carbon monoxide: Overview

On this page

• About carbon monoxide
• Sources
• Higher risk of exposure

About carbon monoxide

Carbon monoxide (also known as CO) is a gas that:

• has no smell, taste or colour
• can only be detected with a carbon monoxide alarm (commonly known as a CO detector)

Exposure to carbon monoxide is dangerous to your health and can cause carbon monoxide poisoning, and even death. Breathing carbon monoxide reduces your body's ability to carry oxygen in your blood and can affect you before you notice its presence.

Carbon monoxide is produced when you burn any type of fuel, and it can be found both indoors and outdoors. It can also help to create ground-level ozone, which is harmful to human health and the environment.

Carbon monoxide is lighter than air and can move freely throughout indoor spaces such as your:

• home
• garage
• shed
• cottage
• camper

Protect your health:

• Know the symptoms of carbon monoxide poisoning.
• Reduce your risk of exposure to carbon monoxide.
• Leave immediately if your carbon monoxide alarm sounds.

Sources

Carbon monoxide is produced whenever you burn fuel like:

• oil
• coal
• butane
• propane
• natural gas
• wood or wood pellets
• gasoline, including in vehicle exhaust

These fuels are commonly used in home appliances, including:

• dryers and hot water tanks
• heating equipment, like:
  • furnaces
  • fireplaces
  • wood and pellet stoves

Carbon monoxide is also produced when you burn tobacco products like cigarettes and cigars.

It’s also produced by fuel-burning equipment and vehicles, including:

• generators
• snowblowers
• wood burning appliances
• lighting equipment, such as lanterns
• outdoor cooking appliances, such as:
  • grills
  • barbecues
  • jet boilers
  • camping stoves
•  vehicles and boat engines
• yard equipment, such as lawn mowers  

Using these devices indoors and in other unventilated or poorly ventilated areas can expose you and others to dangerous levels of carbon monoxide.

Large-scale outdoor sources of human-made carbon monoxide emissions are also produced by:

• the aluminum industry
• on and off-road vehicles, machinery and engines that use:
  • gasoline
  • natural gas
  • other petroleum gases
• the oil and gas industry, notably natural gas production and processing

Wildfires are also large sources of carbon monoxide emissions.

Higher risk of exposure

The risk of exposure to carbon monoxide indoors is greatest in colder months, like in fall and winter. This is because most homes in Canada are heated by appliances that run on  burning fuels.

Indoor appliances

Indoor fuel-burning appliances can release carbon monoxide into your home if they:

• malfunction
• are not properly vented
• are not installed or maintained correctly (like blocked chimney flues)

Some indoor fuel-burning appliances have ventilation systems that run on electricity. Using these appliances during a power outage can cause dangerous levels of carbon monoxide to build up indoors. For example, an electric range hood exhaust fan won’t be able to ventilate the carbon monoxide produced by a gas stove.

Outdoor equipment

You’re also at higher risk of exposure if you use outdoor fuel-burning equipment in indoor areas and in other unventilated or poorly ventilated areas, including during a power outage. These areas include:

• tents
• homes
• campers
• garages or sheds
• cottages or cabins
• outdoor spaces near an air intake