Radon testing in Longueuil

Health Canada's 2012 survey found 8.9% of 112 homes tested in the Région de la Montérégie health region above the guideline. The larger 2024 Cross-Canada survey reports 17.4% (1 in 6) of houses at or above the guideline for Montréal Metro Area (Montréal CMA).

The two surveys aren't directly comparable: the 2024 study pooled about 69,000 volunteer tests and more of them were taken in basements, which partly explains its higher numbers. Neither can tell you about a single house, because neighbouring homes can differ widely.

• Use a long-term test of at least three months, with most of it in the heating season, which gives the most conservative result.
• Place the detector in the lowest level you spend four or more hours a day in, away from drafts, and follow the kit's instructions.
• If the result is above 200 Bq/m³, Health Canada recommends fixing it within a year, sooner if it's much higher.

Our full radon testing guide.

• The Association pulmonaire du Québec sells long-term detectors for about $50 including analysis, and some municipal libraries lend electronic monitors.
• For a professional measurement or mitigation, search the C-NRPP directory by your Longueuil postal code; it lists certified measurement and mitigation professionals.

• Quebec's construction code requires a soil-gas barrier in new dwellings and, since April 17, 2025, a passive radon exhaust stack.
• The Canadian Lung Association's Lungs Matter program offers up to $1,500 toward mitigation for households with low to moderate incomes or a lung cancer diagnosis.
• If your level is high, mitigation (usually a sub-slab depressurization fan system installed by a C-NRPP-certified professional) typically costs $2,000–$4,000.