What is a safe level of radon exposure in the home?

Radon gas is naturally occurring and invisible. It comes from the natural breakdown of uranium in soil and rock and it can get indoors through cracks and other openings in foundation walls. It is the leading cause of lung cancer after smoking. Health Canada has set a guideline for exposure to radon from indoor air. The limit is 200 becquerels per cubic metre of air.

Health Canada recommends that corrective action be taken when this limit is exceeded. The higher the radon level is above this limit, the sooner action should be taken. Health Canada recommends that for levels over 600, the work should be done in less than a year. For levels between 200 and 600, the work should be completed in less than two years.

Testing is simple and relatively inexpensive and should be done using a long-term (three months) test kit during winter months when doors and windows are closed. Radon levels should be tested in areas where people spend more than four hours of the day. Such areas include basement apartments, basement recreation rooms, but would not include basement areas used infrequently such as crawl spaces or laundry rooms. For more information, see Protect Yourself and Your Family, on the Health Canada website.  and our related FAQ: Should I be testing for radon levels in my home?

Last updated June 2012