Glossary · Health & indoor air

Radon test (long-term vs short-term)

Also called: radon testing · long-term radon test · short-term radon test · radon test kit · radon detector · digital radon monitor

Measuring radon with a detector left in the home; long-term tests, over 90 days, give the most reliable yearly average.

What it means

Short-term tests last 2 to 90 days and give a quick snapshot, but radon rises and falls with weather and season. Long-term tests run more than 90 days; Health Canada recommends at least 91 days, ideally 3 to 12 months including the heating season. Place the detector in a regularly used room on the lowest lived-in level, away from kitchens, bathrooms, drafts and the floor.

Why it matters in an audit

Mitigation decisions should rest on a reliable average, and a retest after air sealing or a new HRV shows whether radon changed.

Typical numbers

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

What	Value	Source
Health Canada	At least 91 days, with 91+ days in the heating season; device about 30 cm (1 ft) above the floor and from walls; passive short-term devices aren't suitable for mitigation decisions; hourly readings above 200 Bq/m³ can occur naturally	canada.ca ↗

In Canada

Health Canada says to base decisions on a long-term test, not a passive short-term kit, and on the longest representative average from an electronic monitor rather than hourly spikes.

Sources

Learn more here

Related terms

Radon 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.
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 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.
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.

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