Carbon dioxide in your home

Carbon dioxide (CO₂) is an odourless, colourless and non-flammable gas. Learn about sources of CO₂, its health effects and how to lower exposure to CO₂ in your home.

On this page

• Sources of CO₂ in indoor air
• Health effects of CO₂
• How to lower exposure to CO₂ in your home
• Exposure limit for CO₂ in indoor air in Canada
• CO₂ values in other countries

Sources of CO₂ in indoor air

Carbon dioxide is a pollutant found in indoor and outdoor air.

Indoors, CO₂ is mainly produced through the respiration (breathing) of occupants, but can also come from:

• cigarette smoking
• unvented or poorly vented fuel-burning appliances

The level of CO₂ in indoor air depends on 3 main factors:

• ventilation
• indoor sources of CO₂
• the outdoor CO₂ concentration

The amount of indoor CO₂ is often used:

• as an indicator of general indoor air quality
• to represent ventilation rate (the air changes per hour)

Outdoors, CO₂ comes mainly from:

• forest fires
• combustion of fossil fuels
• animal and plant respiration
• organic matter decomposition

Health effects of CO₂

As CO₂ increases, you may be at increased risk of:

• tiredness
• headache
• eye irritation
• sore or dry throat
• dizziness or difficulty concentrating
• stuffy, congested or runny nose, sneezing, coughing and rhinitis

These effects may not be from CO₂ exposure, but from poor indoor air quality in general.

How to lower exposure to CO₂ in your home

You can lower levels of CO₂ indoors by increasing ventilation and controlling the sources of CO₂.
You can increase ventilation by:

• opening windows when possible
  • check the outdoor air quality conditions in your region before opening windows at Air Quality Health Index
• using mechanical ventilation strategies. You can find more information on how to use both natural and mechanical ventilation to improve indoor air quality.

You can control indoor sources of CO₂ by:

• not smoking indoors
• avoiding crowded living situations, if possible
• using a range hood exhaust fan with outside venting when cooking
• ensuring fuel-burning appliances are in good working order and properly vented
• avoiding the use of unvented fuel-burning appliances (for example, space heaters) indoors

Exposure limit for CO₂ in indoor air in Canada

We developed an exposure limit for CO₂ in Canadian homes based on:

• CO₂ sources
• exposure levels
• the health effects

The long-term exposure limit is 1800 µg/m³ or 1000 parts per million (ppm) based on a 24-hour average. This exposure limit:

• indicates adequate ventilation
• minimizes risks to human health from CO₂ and other indoor air pollutants

This limit protects the health of Canadians including vulnerable populations such as:

• Indigenous peoples
• infants and children
• individuals living in low income housing
• those most susceptible to the effects of CO₂ including individuals with pre-existing health conditions such as:
  • asthma
  • allergies
  • cardiovascular conditions

The recommended exposure limit allows public health officials and other professionals to assess the risk from indoor air pollutants.

CO₂ values in other countries

Canada's long-term exposure limit (1000 ppm) is in line with standards from other countries and organizations.

Countries with established standards or guidelines for CO₂ of 600 to 1000 ppm include:

• Korea
• Japan
• France
• Norway
• Portugal
• Germany

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends maintaining indoor CO₂ levels no greater than 700 ppm above ambient levels (assumed to range between 300 and 500 ppm).

Related information

• Residential indoor air quality guidelines: Carbon dioxide
• Guidance for Cleaner Air Spaces during Wildfire Smoke Events
• Housing suitability
• If you have questions about the guidelines for CO₂ in indoor air, you can contact us at:
  • 1-833-223-1014 (toll free)
  • hc.air.sc@canada.ca