Radon is a radioactive gas that comes from the natural breakdown of uranium in soil and rock. It has no colour, smell or taste, and it can build up inside homes. Elevated radon is found in homes across Alberta, and the only way to know your level is to test. If the result is high, mitigation systems can reduce it substantially.
Why radon matters
When radon is breathed in, its radioactive decay products can damage lung tissue. Health Canada identifies radon as the leading cause of lung cancer in non-smokers and the second leading cause overall. The risk depends on the concentration and how long you are exposed, and it is much higher for people who also smoke.
Radon levels vary from house to house, even on the same street. Soil type, the foundation, cracks and openings, and how the house is heated and ventilated all play a part. A neighbour's result does not tell you yours.
How radon gets in
Houses usually have slightly lower air pressure at the bottom than the soil around them, especially in winter when the heated air inside rises. This draws soil gas, including radon, in through:
- Cracks in the basement floor and walls.
- The joint between the floor slab and foundation wall.
- Sump pits and floor drains.
- Gaps around pipes and wires that pass through the foundation.
- Exposed soil in crawl spaces and unfinished areas.
Energy-efficient, airtight homes are not automatically higher in radon, but how a house is sealed and ventilated affects the result. Testing is the only way to know.
How to test
Health Canada recommends a long-term test of at least three months, ideally during the heating season when windows are closed and radon levels are typically higher. Short-term tests of a few days can give a quick indication, but radon levels change a lot from day to day, so they are less reliable for making decisions.
- Get a long-term detector. Alpha track detectors are commonly used. They are available from retailers, health organizations and radon measurement professionals.
- Place it in the lowest lived-in level of the home, where someone spends at least several hours a day, such as a basement bedroom or family room. Avoid kitchens, bathrooms, laundry rooms and spots near drafts, heat sources or exterior walls.
- Set it at breathing height and leave it undisturbed for the full test period.
- Record start and end dates and send the detector to the lab promptly.
Digital radon monitors are useful for seeing trends but vary in accuracy. For a result to act on, use a long-term test from a reputable lab, or a professional certified under the Canadian National Radon Proficiency Program (C-NRPP).
Understanding the result
Health Canada's guideline for radon in homes is 200 becquerels per cubic metre (Bq/m³). The guideline suggests that the higher the result, the sooner you should act:
- Above 200 Bq/m³: take action to reduce radon, with more urgency at higher levels.
- Below 200 Bq/m³: the guideline does not call for action, but any reduction lowers risk, and some owners choose to mitigate anyway.
Check Health Canada's current guidance for the recommended timelines.
Reducing radon
The most common and effective method is active soil depressurization, sometimes called sub-slab depressurization. A pipe is installed through the basement floor and connected to a fan that draws soil gas from under the slab and vents it outdoors, above the roofline or as the installer's standards require. Sealing major cracks and openings, covering sump pits and improving crawl space ground covers help, but on their own are often not enough.
Mitigation should be done by a C-NRPP certified mitigation professional. After installation, re-test to confirm the system works, and test again every few years or after major renovations.
Newer homes may have been built with a radon rough-in, a capped pipe through the slab that makes installing a system easier. Building code requirements have changed over time, so check what applies to your home.
How ehZee can help
During an ehZee home inspection, we look at the basement and foundation for openings that let soil gas in, note whether a radon rough-in or mitigation system is present, and recommend testing. You can walk through with the inspector and get a written report within two days. Related reading: why basements leak and what to look for in a crawl space.
Common questions
Can I test for radon during a home purchase?
A long-term test usually takes longer than a purchase timeline allows. Some buyers do a short-term test as an indication and plan a long-term test after moving in, or negotiate with the seller on testing and mitigation.
Do apartments need radon testing?
Units on the lowest floors and in basements have the greatest potential for elevated radon. Units higher up are generally lower, but testing is the only way to know.
Is radon only a problem in some parts of Alberta?
Elevated levels have been found in homes across the province. Every home should be tested regardless of location.