Glossary · Health & indoor air

Radon

Also called: radon gas · radon-222 · radon level · radon levels

A natural radioactive gas from uranium in soil and rock that can build up in homes; long-term exposure raises the risk of lung cancer.

What it means

You can't see, smell or taste radon, so testing is the only way to know your level. It enters through foundation cracks, sumps, floor drains and gaps around pipes, drawn in by the stack effect and depressurization. Canada and the US use different units and action levels (see radon units).

Why it matters in an audit

Air sealing and ventilation changes affect radon, so a radon test before or after upgrades belongs in any audit, and fixing high levels usually costs about as much as other common home repairs.

Typical numbers

Reference values with their sources. Your energy advisor’s report gives the figure for your own house.

What	Value	Source
Health Canada guideline	200 Bq/m³ (annual average in a normally occupied area); act within 1 year if above, sooner if much higher, and keep levels as low as reasonably achievable	canada.ca ↗
Canadian homes above the guideline	6.9% of Canadians in Health Canada's 2009–2011 survey; a 2024 study cited by Health Canada found 17.8% of houses at or above 200 Bq/m³	canada.ca ↗

In Canada

Health Canada's guideline is 200 Bq/m³; use a long-term test of at least 91 days, ideally during the heating season.

Sources

Learn more here

Related terms

Radon units: Bq/m³ and pCi/L Canada measures radon in becquerels per cubic metre (Bq/m³) and the US in picocuries per litre (pCi/L); 1 pCi/L equals 37 Bq/m³.
Radon test (long-term vs short-term) Measuring radon with a detector left in the home; long-term tests, over 90 days, give the most reliable yearly average.
Radon mitigation (sub-slab depressurization) Fixing high radon, usually with a pipe through the basement floor and a fan that pulls soil gas from under the slab and vents it outside.
Stack effect Warm indoor air rises and escapes near the top of a house, pulling cold outside air in near the bottom; it's strongest on cold days.
Depressurization When more air is being pushed out of a house than is coming in, so the inside sits at slightly lower pressure than outdoors.
Radon guideline (200 Bq/m³) Health Canada's radon guideline: fix your home if the yearly average where people spend time is above 200 Bq/m³, within a year, and sooner if higher.
C-NRPP (Canadian National Radon Proficiency Program) Canada's certification program for radon professionals; Health Canada recommends a C-NRPP certified professional to fix high radon.
Health region (radon survey area) The public health area a radon survey reports by, such as a BC Health Service Delivery Area; results describe a region, not your home.

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