What does my radon test result mean? Common questions
Sourced answers on what your radon result means: safe levels, above or below 200 Bq/m³, a result near the guideline, a neighbour's test and floor level.
Understanding your result
What is Canada's radon guideline?
Canada's radon guideline is 200 Bq/m³.
Health Canada recommends corrective action when the yearly average radon level is above 200 Bq/m³ in a normal occupancy area. It says the health risk below the guideline is small. It also says no level of radon exposure is considered risk free.
What should I do if my home is above 200 Bq/m³?
Take corrective action within one year.
Health Canada recommends acting sooner the higher your radon level is. It also recommends lowering the level as far as is reasonably practicable. Getting below 200 Bq/m³ does not end that advice: if you can reasonably go lower, Health Canada recommends you do.
Does a result below 200 Bq/m³ mean my home is completely safe?
No.
Health Canada states that the health risk below 200 Bq/m³ is small, but no radon level is considered risk free. Any action that lowers your exposure lowers your risk.
Health Canada uses 200 Bq/m³ as the point where it recommends corrective action. The guideline does not divide safe homes from unsafe ones.
My result is close to 200 Bq/m³. How precise is that number?
Not exactly. Every radon measurement carries some uncertainty.
If you repeat the same test under the same conditions, the result may come out a little different. Health Canada notes that North American standards from the Canadian Standards Association and the American National Standards Institute accept repeated detector results that vary by up to 25%.
A result slightly above 200 Bq/m³ may reflect a true level below the guideline. A result slightly below 200 Bq/m³ may reflect a true level slightly above it. Health Canada's advice still applies to the number you measured: act on results above the guideline.
My neighbour tested low. Does that mean my home is probably low too?
No.
Health Canada states that radon can vary widely between homes, even homes in the same building or on the same street. Geology, foundation construction, entry points, ventilation and building design all affect how much radon gets into a building and stays there. The only way to know your home's level is to test your home.
Is there a part of Canada where radon testing isn't necessary?
No.
Health Canada recommends testing every home, no matter where it is or what type of building it is. The 2024 Cross-Canada Radon Survey found no part of Canada that is radon free. Its authors state that the results should not be used to decide whether to test a specific home.
How common is elevated radon in Canada?
About 1 in 5 single-detached, semi-detached and row homes, or 17.8%, is at or above 200 Bq/m³, according to the 2024 Cross-Canada Radon Survey (Version 1.1).
The survey weighted 69,478 unique long-term test results by region, community type and building type. It found a geometric average home radon level of 84.7 Bq/m³. Another 24.2% of these building types were between 100 and 199 Bq/m³, so 42% are at or above the World Health Organization reference level of 100 Bq/m³.
The 2012 survey reported 6.9% at or above 200 Bq/m³, but the figures do not compare directly. The 2012 survey used about 14,000 results, drew on different data sources and did not use this weighting.
Does the Canadian average tell me the radon level in my home?
No.
A national or regional average cannot tell you the level in any one building. The authors of the 2024 Cross-Canada Radon Survey say so themselves. They state that its results should not be used to judge your personal radon risk.
Does the floor where I test matter?
Yes.
Health Canada recommends testing the lowest lived-in level, in a room where someone spends more than four hours a day. The 2024 Cross-Canada Radon Survey found that tests in rooms below ground averaged 23.5% higher than tests in ground-level rooms. Ground-level rooms averaged 20.9% higher than rooms at least one storey up. That is a population average, not a rule about any one house.
The survey also found that the share of tests placed below ground rose from 31% in 2012 to 68% in 2024. It suggests this reflects more use of lower levels as living space, such as basement suites. That shift may explain part of the difference between the two surveys.