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Posted by on Aug 2016 in All Stories, Member Support | 0 comments

Radon gas: What housing providers need to know

Radon distribution in Ontario

Radon distribution in Ontario

What is radon?

Radon is a naturally occurring colourless and odourless radioactive gas created from the radioactive decay of uranium, which is commonly found in the earth’s crust. Radon enters buildings through cracks in basement floors, drains, sump pits, exposed soil, construction joints and more. Once radon has entered a building, it can easily be inhaled, increasing an individual’s risk of lung cancer.

The allowable exposure for radon prescribed by Health Canada is 200 Becquerels per cubic metre of air (Bq/m3), which is higher than the United States Environmental Protection Agency (EPA) and the World Health Organization (WHO) action levels of 148 Bq/m3 and 100 Bq/m3, respectively. As with all cancer causing agents, exposure should be reduced to As Low As Reasonably Achievable (ALARA) levels. Health Canada has estimated that about seven per cent of Canadians are living in homes above the radon guideline of 200 Bq/m3. [1]

Tenancy and radon

On March 14, 2016, the Ministry of Municipal Affairs and Housing announced the details of its Long-Term Affordable Housing Strategy (LTAHS) Update. Section 3.3 of the strategy explores opportunities to protect Ontario’s tenants from the potential health-related impacts of radon. It states that:

“Health agencies have noted that when radon enters an enclosed space, which is not properly ventilated (e.g., a basement or houses in winter), it can accumulate to high concentrations over the long-term, and lead to increased lifetime risk of developing lung cancer. As a result, some stakeholders have voiced concerns regarding the potential presence of radon in basement apartments.”[2]

It’s important to note that radon can enter a building regardless of the season. Radon levels routinely exceed the 200 Bq/m3 action level, even when buildings are properly ventilated. Health Canada clearly states that the only way to determine a building’s radon level is to test for it, and that all buildings should be tested.

How to test for radon

Radon testing is conducted by using a small sampling device in the lowest lived-in level of a building, and leaving it undisturbed for 3 to 12 months.

The long sample durations account for fluctuations in radon concentrations from daily and seasonal weather, occupant activity, and other variables. The results are then compared to the 200 Bq/m3 action level. If the building has elevated radon concentrations, measures to reduce the concentration should be implemented within a reasonable time frame (typically 1 to 2 years).

How to mitigate radon levels

The most effective and perhaps preferred method of mitigation is sub-slab depressurization (SSD). This involves coring holes through the basement floor and installing piping and an air tight in-line fan thereby preventing the radon from entering the building and venting it outdoors. Radon measurement providers and mitigation contractors should be properly insured and certified by the Canadian National Radon Proficiency Program (C-NRPP).


[1] Health Canada, Cross-Canada Survey of Radon Concentrations in Homes Final Report, March 2012




Bruce Decker, C.E.T., ROHT, BSSO
C-NRPP Certified
Senior Technical Advisor, Building Health Sciences, QA  | 519-743-6500 ext. 1321

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