Radon Action Month: how to test your home this winter

Nearly one in five Canadian homes has radon levels at or above Health Canada’s guideline, and with November marking Radon Action Month, health officials say the coming cold months are the best time to find out whether yours is one of them.

Radon is an invisible, odourless radioactive gas that seeps out of the ground and can build up indoors, especially in basements. Health Canada calls it the leading cause of lung cancer among people who have never smoked, and the second leading cause overall after smoking.

The latest national picture comes from the 2024 Cross-Canada Survey of Radon Exposure, led by researchers at the University of Calgary. It found that about 17.8 per cent of houses are at or above Health Canada’s guideline of 200 becquerels per cubic metre (Bq/m³), more than double the roughly seven per cent found in a 2012 federal survey. Results vary widely by region: the survey found about one in three properties in Atlantic Canada and in the Pacific Interior and Yukon at or above the guideline, compared with about one in 75 on the Pacific coast.

Health Canada advises testing for at least three months, ideally in the fall or winter when windows and doors stay closed and indoor radon tends to be highest. The test should go in the lowest level of the home where someone spends at least four hours a day, such as a finished basement or a ground-floor bedroom.

The most common option is a long-term test kit. It is placed in the home for about three months and then mailed to a lab, which sends back a single average reading. Kits are sold by hardware stores, provincial lung associations and some public health units, and some regions run free or low-cost testing programs during Radon Action Month.

Digital radon monitors are a newer choice. They display readings continuously and can stay in a home for years, which lets owners see how levels change with the seasons, the weather and ventilation. Health Canada’s advice is to buy only monitors that have passed performance testing by the Canadian National Radon Proficiency Program (C-NRPP), which publishes a consumer report listing approved models. C-NRPP also recommends following up with a long-term test if a digital monitor has been used for less than 91 days.

That caution follows a string of recalls. Since 2022, Health Canada has recalled or warned about several inexpensive radon detectors sold online, mainly through Amazon.ca, including models from Air Steward, Life Basis, InkBird, Spolehli and Hanchen, after its testing found they measured radon inaccurately. In one case, the department said a device could report a low value regardless of the actual radon level. Owners of recalled devices are told to stop using them.

One of the monitors on C-NRPP’s approved list is made by Aranet, which listed it as the Aranet RN+ and markets it in Canada as the Aranet Radon Plus. The company says the battery-powered device gives a first reading within about 10 minutes, runs for up to seven years on two AA batteries, shows a colour-coded level on its screen and does not need an account or subscription. C-NRPP’s report lists its accuracy at plus or minus eight per cent for 24-hour, seven-day and 30-day averages. Other approved models are listed in the same report.

If a test comes back high, Health Canada recommends reducing radon levels with help from a C-NRPP-certified mitigation professional, usually by sealing entry points and installing a system that vents the gas from under the foundation. The department advises acting within two years for levels between 200 and 600 Bq/m³, and within one year for levels above 600 Bq/m³.

Sources: Health Canada, University of Calgary, C-NRPP consumer monitor report, Health Canada recalls and advisories.

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