Radon cannot be seen or smelled. It must be measured.
Radon is a naturally occurring radioactive gas that can accumulate in buildings. Health Canada identifies it as the second leading cause of lung cancer after smoking and the leading cause among non-smokers.
To determine whether a home exceeds Canada’s 200 Bq/m³ guideline, use a long-term test for at least three months during the heating season on the lowest regularly occupied level.
Why every home should be tested
Concentrations can differ significantly between neighbouring buildings. Foundation type, entry routes, ventilation, indoor pressure and soil all influence the result. Age, appearance and a visual inspection cannot predict concentration.
How to test properly
Health Canada recommends long-term testing for at least three months, ideally in fall or winter. Place the detector on the lowest occupied level where someone spends at least four hours per day, following device instructions. Use a laboratory, device or professional recognized by the Canadian National Radon Proficiency Program (C-NRPP).
What does 200 Bq/m³ mean?
Canada’s guideline is 200 becquerels per cubic metre. Above this annual average, Health Canada recommends mitigation within one year and sooner as concentrations rise. No level is completely risk-free, however, and reducing exposure remains beneficial.
Short-term or long-term test?
A short test lasting a few days may help verify a mitigation system after work, but it varies more with weather and occupancy. Health Canada says it should not be used alone to decide whether a home exceeds the guideline; long-term measurement is the reference.
What if the result is high?
Active sub-slab depressurization is a common and generally effective method: a fan exhausts soil gas before it enters the building. The solution depends on the foundation and must be designed correctly. Use a C-NRPP-certified professional and perform follow-up testing.
The building inspector’s role
An inspector can explain the issue, observe some foundation characteristics and recommend testing. A point-in-time inspection does not replace a three-month measurement. La facture’s reporting likewise underscores that this invisible risk is resolved through measurement, not guesswork.
Sources and references
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