The Canadian guideline: 200 Bq/m³
Health Canada sets the indoor radon action level at 200 becquerels per cubic metre (Bq/m³), measured as a long-term annual average. Above this level, you should reduce radon — within two years for readings of 200–600 Bq/m³ and within one year for readings above 600 Bq/m³. This is not a "safe vs unsafe" line: it's the level at which mitigation becomes cost-effective relative to the lifetime lung-cancer risk it prevents.
The WHO reference: 100 Bq/m³
The World Health Organization recommends a more conservative reference level of 100 Bq/m³, citing epidemiological evidence that lung-cancer risk rises measurably below the Canadian threshold. Many European countries have adopted the WHO figure. Practically, if your home tests between 100 and 200 Bq/m³, you're under the Canadian action level but the WHO would still flag it.
Bq/m³, pCi/L, and the U.S. EPA action level
Canada and most of the world use becquerels per cubic metre (Bq/m³). The United States uses picocuries per litre (pCi/L). The conversion is straightforward:
- 1 pCi/L = 37 Bq/m³
- Health Canada 200 Bq/m³ ≈ 5.4 pCi/L
- U.S. EPA action level 4 pCi/L ≈ 148 Bq/m³
- WHO reference 100 Bq/m³ ≈ 2.7 pCi/L
If you bought a U.S.-market detector, check whether it reports in pCi/L and convert before comparing to Canadian guidelines.
The Canadian average
Health Canada's cross-Canada survey of more than 17,000 homes found a national average of roughly 95 Bq/m³, with about 7% of homes above the 200 Bq/m³ action level. Provincial and FSA-level averages vary substantially. Look up your postal code to see how your area compares.
What your reading means
- Below 100 Bq/m³ — below both Canadian and WHO references. No action needed; consider retesting every few years.
- 100–200 Bq/m³ — below Canadian action but above WHO reference. Reduce where practical; long-term real-time monitoring helps track variation.
- 200–600 Bq/m³ — above the Health Canada action level. Mitigate within two years.
- Above 600 Bq/m³ — significantly elevated. Mitigate within one year.
Important caveats
Radon fluctuates dramatically with weather, season, and ventilation — single short-term readings can be off by 2–3x compared to the true annual average. Always base mitigation decisions on a long-term (91+ day) test or a real-time monitor's long-term average, not a single spot reading.
Frequently asked questions
What is a safe radon level in Canada?
Health Canada's action level is 200 Bq/m³ — readings above this should be mitigated. The World Health Organization recommends a more conservative reference of 100 Bq/m³. There is no truly 'safe' level; risk rises continuously with exposure.
How do I convert Bq/m³ to pCi/L?
Divide Bq/m³ by 37 to get pCi/L. The Canadian 200 Bq/m³ guideline equals about 5.4 pCi/L. The U.S. EPA action level is 4 pCi/L (≈148 Bq/m³).
What is the average indoor radon level in Canada?
The Health Canada cross-Canada radon survey reports a national average of roughly 95 Bq/m³, with about 7% of homes above 200 Bq/m³. Averages vary widely — some FSAs exceed 300 Bq/m³ on average.
Is 100 Bq/m³ safe?
It is below Canada's action level but above the WHO reference. Lung-cancer risk is still present and rises with years of exposure — reducing it where practical is worthwhile.
Where in Canada has the highest radon?
Saskatchewan, Manitoba, the Yukon, New Brunswick, and parts of southern Ontario and Quebec report elevated regional averages. Use the radon map to see by postal code.
Keep learning
Long-term vs real-time monitoring — the only way to know your number.
What to do once your reading exceeds 200 Bq/m³.
Why these thresholds matter for long-term lung-cancer risk.
See how your postal code compares to the national average.