Topic Overview

What is radon?

Radon is a radioactive gas that causes cancer. Radon is found in rock, soil, water, some building materials, and natural gas. You can't see, taste, or smell it.

How does radon exposure occur?

Any home, school, office, or other building can have high levels of radon. Radon is found in new and old buildings. It can seep in through any opening where the building contacts the soil. If a house's water supply contains radon, radon may enter the air inside the house through pipes, drains, faucets, or appliances that use water. Then the radon may get trapped inside the house.

Studies show that nearly 1 out of 15 homes in Canada has unsafe levels of radon.footnote 1 If you live in an area that has large deposits of uranium, you may be more likely to be exposed to high levels of radon. But the construction features and exact location of your house may be just as likely to affect your risk. Even houses right next to each other can have very different radon levels.

What are the health effects of radon exposure?

Over time, exposure to radon can cause lung cancer. Radon causes about 4,000 lung cancer deaths each year in Canada. It is the second leading cause of lung cancer, after tobacco smoking.footnote 1 People who smoke have an even higher risk of lung cancer from radon exposure than people who don't smoke.

Radon exposure doesn't cause symptoms. Unless your home or office is tested for high radon levels, you may not realize that you are being exposed to dangerous levels of radon until you or someone in your family is diagnosed with lung cancer.

How can you test your home's radon levels?

Health Canada recommends that all homes be tested for radon levels.

You can hire a qualified tester to do the test, or you can use a do-it-yourself test kit. You can buy radon test kits on the Internet or from home improvement stores. You can also contact your provincial environmental office for advice. There are short-term and long-term tests available. Both measure radon levels in the air. But Health Canada only recommends the use of the long-term test.

  • The short-term test kit stays in your home or office for 2 to 90 days. Radon levels vary daily and from season to season. So you may want to follow up the first short-term test with a second test.
  • The long-term test kit stays in your home or office for more than 90 days. A long-term test will give more accurate results.

Health Canada recommends placing the test kit in your home on the lowest level that you regularly use. If you have questions about radon in your house, you can get help from Health Canada by calling 1-855-809-6966.

How do you reduce high levels of radon?

If tests find a high level of radon, you'll need to reduce it. There are two parts to this:

  • Preventing radon from entering the building. The most common way to do this is through sub-slab depressurization, which vents air from beneath the foundation. This work should be done by a qualified contractor. Other control methods include sealing cracks in the foundation or walls and using house or room pressurization.footnote 2
  • Venting radon out of the building. Once the radon is prevented from entering the building, venting can be done to reduce the level of radon. These may include using fans, blowers, and suction devices to remove radon in the air in crawl spaces, basements, and other areas.

Health Canada recommends that you use a contractor certified by the Canadian National Radon Proficiency Program (C-NRPP). Hire a contractor with proper training in radon reduction to help with this work. For a list of certified radon professionals in your area, you can call C-NRPP at 1-855-722-6777 or go to

After radon reduction or prevention procedures are done, the home or building should be retested. You may need to retest more than once. It is usually safe to live in the home or building while the radon is being vented, but you may want to confirm this with your provincial environmental office.

For general information about removing or reducing radon in your house, you can call your provincial environmental office or go to the Health Canada website at for more information.

Other Places To Get Help


Health Canada

Related Information



  1. Health Canada (2012). It's your health: Radon. Available online:
  2. U.S. Environmental Protection Agency (2010). Consumer's Guide to Radon Reduction. Available online:


ByHealthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Donald Sproule, MDCM, CCFP - Family Medicine
Adam Husney, MD - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care Medicine, Medical Toxicology

Current as ofNovember 20, 2015