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Indoor Air Quality



  • Mold
  • Carbon Monoxide
  • Radon
  • Protecting your Health
  • Things You Can Do to Improve Indoor Air Quality
  • Residential Indoor Air Quality Guidelines 
  • Healthy Indoors Partnership

Most people are aware that outdoor air pollution can damage our health, but fewer realize that indoor air pollution can be as or even more harmful. Studies by Health Canada, the US Environmental Protection Agency and other agencies indicate that levels of several indoor air pollutants may be significantly higher than outdoor levels. Since Canadians spend about 90 percent of their time indoors, the quality of indoor air is a significant concern.

Indoor air quality is the result of complex interactions among buildings, building systems and people. Over the past several decades, people's exposure to indoor air pollution has increased due to a variety of factors. These include:

  • the construction of more tightly sealed buildings without sufficient air exchange;
  • reduced ventilation rates to save energy;
  • the use of synthetic building materials and furnishings;
  • the use of chemically formulated personal care products;
  • the use of pesticides and housekeeping supplies;
  • the increased complexity of modern building systems; and
  • building deterioration due to age, improper maintenance or design.

Mold, carbon monoxide and radon are three of the most serious contaminants affecting indoor air - each of these can have serious impacts on our health.

Unhealthy air in your home, school or workplace can cause a number of health problems, such as asthma, allergies, coughing, wheezing, dizziness, nausea, headaches, inability to concentrate, short-term memory loss and hyperactivity. Children may be especially susceptible.

To find out how to minimize the health risks related to poor indoor air quality..

Health Canada continues to work with others to improve the quality of indoor air. Activities include:

  1. Residential Indoor Air Quality Guidelines
  2. Indoor Air Quality Tools for Schools Action Kit
  3. Healthy Indoors Partnership


Molds are fungi that grow in damp environments. Mold spores contain allergens and irritants that often cause people living in houses where molds grow to suffer from allergic reactions and respiratory diseases.

Humid or damp conditions in your home can encourage the growth of mold and dust mites. Mold can develop from poor ventilation, flooding and building leaks. It can also grow in humidifiers, air conditioners, refrigerator drip pans and damp basements, on bathroom surfaces and behind furniture placed against outside walls or window frames. Moldy smells from basements, carpets and gypsum board are a sign that they harbour fungi.

Health Canada and the Canada Mortgage and Housing Corporation are working on research to find out how mold, dust mites, bacteria and other contaminants can affect your health.

For more information on how to both prevent mold and get rid of existing mold in your home, visit the CMHC Homeowner's Guide to Fighting Mold.

Carbon Monoxide

Carbon monoxide is a colourless, odourless gas produced by the incomplete burning of any material containing carbon, such as propane, gasoline, oil, natural gas, coal or wood.

Possible sources of carbon monoxide in the home are:

  • gas and oil furnaces and appliances that are not properly maintained or vented to the outside of the building;
  • car engines in attached garages; and
  • tobacco smoke.

The first symptom of carbon monoxide poisoning is usually a headache with throbbing temples. Other initial symptoms are tiredness and shortness of breath, tightness across the forehead, flushed skin and slightly impaired motor skills.

As the carbon monoxide level or exposure time increases, symptoms become more severe: irritability, chest pain, fatigue, diminished judgment, dizziness and dimness of vision. Still higher levels cause fainting upon exertion, marked confusion and collapse. If exposure continues, coma, convulsion and death from respiratory arrest can result.

For more information on carbon monoxide and preventing exposure, read Canada Mortgage and Housing Corporation's fact sheet on carbon monoxide.


Radon is a colourless, odourless radioactive gas that occurs naturally in our environment. It comes from the natural breakdown (radioactive decay) of uranium. Radon can be found in high concentrations where soils and rocks contain uranium, granite, shale or phosphate. Radon may also be found in soils contaminated with certain types of industrial waste, such as the by-products of uranium or phosphate mining.

Is Radon Dangerous?

Protecting your Health


If there is mold growing in your home, Health Canada's recommendation is to have it remediated promptly in order to reduce the risk of possible health problems in your family. Remediation includes identifying the extent of the mold, solving the underlying moisture problem and removing the mold under safe conditions. Mold grows only on materials that have become damp or wet because of, e.g. excessive humidity, pipe leaks, infiltration from the outside, or flood.

The Canada Mortgage and Housing Corporation (CMHC) offers information about dealing with moisture and mold in your home. You may check their web site for various sources of information on these subjects, including Fighting Mold, or contact CMHC at 1-800-668-2642.

If you need assistance to determine whether there is mold growing in your house, the extent or the cause of the problem, then having your home inspected by a qualified indoor air quality investigator is usually the best option. CMHC offers indoor air quality training to qualified individuals and maintains a list of those who have successfully completed the training. You may contact CMHC to find qualified investigators working in your area.

In the event of a flood, take action immediately to remove the water and wet porous materials and contents. For more detailed information, contact CMHC at 1-800-668-2642 or check their guide entitled After the Flood. Drying your house and furnishing within 24-48h will reduce or prevent mold growth and greatly lessen repair costs.


  • Ensure all gas- and oil-burning cooking and heating appliances are properly maintained and inspected annually by a qualified technician.
  • Purchase a carbon monoxide detector.
  • Never use an un-vented combustion appliances or any appliance designed for outdoor use (such as a kerosene space heater, barbecue, propane stove, etc.) in your home.
  • If you have a garage attached to your house, never use a remote starter when your car is inside it. Never start your car when the door between your garage and your home is open.
  • Check your fireplace to make sure the flues are open before lighting a fire. If the chimney doesn't draw, call a fireplace professional.
  • Never use barbecues indoors, in an attached garage or any other enclosed area.
  • Never run lawnmowers, snow blowers or gas trimmers inside an attached garage or enclosed area.
  • Avoid using kerosene heaters indoors or in a garage, unless it is meant to be used inside

Avoid and/or Contain Other Contaminants

  • Keep your home clean and dust-free.
  • Don't let anyone smoke in your home.
  • Minimize the use of potential contaminants by finding substitutes or eliminating them altogether.
  • Clean (or report) any spills or leaks.
  • If working in a contaminant-producing area, ensure contaminant sources are contained (e.g. work under fume hoods, clean up spills, keep doors and windows closed).
  • Take your shoes off when you enter the house. The soil outside your home can contain a number of substances you do not want inside.

If you have severe humidity or contamination problems, ask your provincial or regional health department for advice. Talk to your doctor if you think anyone in your family suffers from health problems caused by poor air quality.

Residential Indoor Air Quality Guidelines

The Residential Indoor Air Quality Guidelines are a tool available for those who work to ensure safe residential environments, such as medical officers of health and public health inspectors. These guidelines were developed by the Federal/Provincial Advisory Committee on Environmental and Occupational Health (CEOH) and published in 1987.
To view the full guidelines, 

Things you can do to improve indoor air quality

  • Maintain your heating and air conditioning systems regularly.
  • Keep carpets and flooring dust-free.
  • Maintain a relative humidity below 50% to prevent mold growth.
  • Avoid using a chemical cleaner when a natural one will do.
  • Make sure there is a steady supply of fresh air.  The more the air can move around the better.
  • Avoid smoking indoors.

Healthy Indoors Partnership

Health Canada is a member of the Healthy Indoors Partnership, a multi-sectoral, not-for-profit organization created to foster cooperation and communication among organizations and individuals who want to improve indoor air quality for Canadians. Partners include federal government departments, non-government organizations, academics, industry and consumer groups.

Source: Health Canada