Radon: Reducing your risk at home

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Learn the facts about radon, what it is, health risks, and practical tips on reducing radon exposure in the home.

Key points

  • Radon is a colourless, odorless, radioactive gas that occurs naturally in the environment. It occurs in the air outdoors in such small amounts that it is not a health risk.
  • Radon can enter into homes through floors, cracks in concrete walls and basement drains. In closed spaces, like basements, radon can build up to relatively high levels.
  • Breathing in radon gas or the products that is produces when it decays may increase the risk of developing cancer.
  • You should check for radon in your home by testing for it. There are both short- and long-term steps you can take to reduce the levels of radon in your home.

Radon is a colourless, odorless, radioactive gas. It is produced during the natural breakdown of the chemical element, uranium, which is found in soil, rocks and groundwater. As a result, radon occurs naturally in the environment.

Radon occurs in outdoor air in such small amounts that it is not a health risk in the open air.

Radon in the home

Radon can easily escape from the ground into homes through floors, cracks in concrete walls, and basement drains. Levels in the home are usually higher in basements, cellars, or other structural areas in contact with soil. In closed spaces, like basements, radon can build up to relatively high levels. This is when it may pose a risk to your health.

How does radon affect your health?

By breathing in alpha particles

Radon is radioactive, meaning it decays. As it decays, it produces many products, some of which emit cancerous particles. These are called alpha particles. They bind easily to air dust and other particles in the air.

Each time we inhale, air goes into the nose or mouth, and through the windpipe. The windpipe connects the nose and mouth to our lungs. If breathed in, alpha particles can damage the tissue inside our trachea and lungs.

Alpha particles may cause lung cancer

Radon is the second leading cause of lung cancer, next to smoking. According to Health Canada, on average about 10% of the lung cancers worldwide are linked to radon exposure.

The risk of developing lung cancer increases:

  • the more radon a person is exposed to
  • the longer a person is exposed to radon

Also, radon is much more likely to cause lung cancer in people who smoke.

Are children at greater risk?

It is unclear. Some experts say because children breathe faster and have smaller lungs, they may absorb higher doses of radon and at faster rates compared to adults. But according to the Environmental Protection Agency, there is no evidence that children are at greater risk when exposed to radon.

Regardless, studies linking radon exposure to lung cancer have been well studied. All experts agree that everyone should take steps to reduce radon exposure in the home.

Should all homeowners test for radon levels?

Yes, according to Health Canada. In 2009, Health Canada initiated a two-year study to assess radon levels in Canadian homes. In the first year of the study, researchers analyzed 9,000 homes. Early results show that about 7% of these houses have "elevated levels" of radon.

How do I know if I have radon in my home?

The only way to check for radon in your home is to test for it.

Most homes will contain some levels of radon; the concern is how much. It is not possible to predict levels of radon in homes. There are many factors involved. House location and its relation to the wind, for instance, are just as important as the source of radon.

Purchase a commercial device that measures radon levels

Most hardware or home improvement shops carry radon testing devices. Look for one that measures radon levels in the long term (at least three months). Otherwise, you can buy one online.

Commonly used devices to measure radon levels in the home include:

  • charcoal canister: charcoal inside this container absorbs radon gas
  • electrets ion detector: this device contains a Teflon disc that collects charged radon products
  • alpha track detector: this device contains a plastic film which traps alpha particles

Follow the instructions that come with the device. In general:

  • Place the device in the lowest part of your house that you use often. For example, your basement or your main floor.
  • Make sure it is placed in a safe corner, where no one can accidently push it over
  • Leave the device there for three months.
  • After the testing is complete, mail it back to the company laboratory for analysis. They analyze the radon test device and mail you the results.

When is the best time to test for radon?

It is a good idea to run the test during the winter, when there is generally less ventilation in the home.

What the test results mean

The amount of radon in the air is measured in units called becquerels per cubic meter (bq/m3). According to Health Canada’s radon guidelines:

  • If radon levels in your home are less than 200 Bq/m3, you do not need to do anything. But even with such low levels, continue to reduce the amount of radon gas in your home (see below for tips).
  • If radon levels in your home are between 200 Bq/m3 and 600 Bq/m3, take steps to reduce radon levels in your home within the next two years.
  • If radon levels in your home are over 600 Bq/m3 take steps to reduce radon levels in your home within one year.

How do you reduce radon levels in your home?

There are short-term steps you can take:

  • Seal cracks and holes found in walls, floors, drains and pipes. This can help minimize radon from seeping into living rooms from the basement.
  • Renovate existing basement floors, particularly earth floors.
  • Increase ventilation in the subfloors beneath the basement.
  • Install a device that sucks the radon from the lowest space in the basement (radon sump system).
  • Avoid using exhaust fans for a continuous amount of time.
  • When you are not using the fireplace, shut the chimney damper.

Longer-term solutions require a lot more work. You may need to call a contractor to perform these fixes.


For more information about radon exposure in Canada:

  • Visit the Health Canada’s Radon Protection Bureau website. In Ontario, email Radon_Ontario@hc-sc.gc.ca; call 416-973-4389 or toll-free at 1-866-999-7612.
  • Call Health Canada toll free at 1-866-225-0709 or 1-800-267-1245. You can also request a copy of Health Canada’s radon guideline booklet: Radon — A Guide for Canadian Homeowners.


Radon and health fact sheet. World Health Organization: Radon Factsheet. Retrieved from https://www.who.int/en/news-room/fact-sheets/detail/radon-and-health.

Radon. Health Canada. Retrieved from https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon.html.

Cross-Canada Survey of Radon Concentrations in Homes — Final Report. Health Canada. Retrieved from https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/cross-canada-survey-radon-concentrations-homes-final-report-health-canada-2012.html.

Radon. The Lung Association. Retrieved from https://www.lung.ca/lung-health/air-quality/indoor-air-quality/radon.

Last updated: November 28th 2011