What is a safe radon level?

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. Any home above this level should take corrective action to lower radon within one year. The higher the radon concentration, the sooner you should act — readings well into the thousands require immediate intervention. 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 initial 2012 Cross-Canada Radon 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.
• Above 200 Bq/m³ — above the Health Canada action level. Mitigate within one year; act sooner when concentrations are very high.

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.