Radon is one of those topics that doesn't come up at dinner parties. It's invisible, it has no smell, and you'd never know it was there. But if you live in the West Kootenays, it's worth five minutes of your attention, because fall is the perfect time to do something about it.
What is radon?
Radon is a radioactive gas that forms naturally when uranium in rock and soil breaks down. It seeps up through the ground and can collect inside homes, especially in basements and ground floors.
Outdoors, it disperses harmlessly. Indoors, it can build up. Long-term exposure to high levels is the second leading cause of lung cancer in Canada, after smoking, and the leading cause for people who've never smoked.
Why it matters here
Geology is the big factor, and BC's Interior has a lot of the wrong kind. The BC Centre for Disease Control notes that radon levels are generally higher in the Interior than in other parts of the province. Reporting in 2026 found that roughly one in three tested Interior homes came in above Health Canada's guideline.
Closer to home, a 2024 community testing program in Kaslo found about 13% of homes above the guideline, and the West Kootenay region, Castlegar in particular, has long been flagged for elevated levels. Levels can vary widely even between neighbouring houses, so your neighbour's test result doesn't tell you much about yours.
The magic number: 200
Health Canada's guideline is 200 becquerels per cubic metre (Bq/m³). If your long-term test comes in above that, Health Canada recommends taking action to bring it down. The higher the number, the sooner you should act.
Why fall and winter are best for testing
Radon levels are usually highest when houses are closed up and the heat is running. That makes the cold months the most accurate time to test. Health Canada recommends a long-term test of at least three months, which means a test started in October or November gives you a reliable answer by early spring.
How to test
It's easier than most people think.
- Buy a long-term test kit. They're available online through groups like the BC Lung Foundation, Interior Health's radon page and some local hardware stores.
- Place it in the lowest lived-in level of your home. That's where you spend at least four hours a day, like a basement family room or a ground-floor bedroom.
- Leave it for at least 91 days. Don't move it.
- Mail it to the lab. You'll get your results by email.
Digital monitors are also available and give you running readings. They're handy, but a lab-analysed long-term test is still the standard to rely on.
What if your number is high?
Don't panic. Radon is very fixable. The most common solution is called sub-slab depressurization. A certified mitigation professional installs a pipe through the basement floor and a small fan that draws radon from under the house and vents it outside. Levels often drop dramatically.
Look for a professional certified through the Canadian National Radon Proficiency Program (C-NRPP). Costs vary by home, but it's typically less than many common renovations. The Canadian Lung Association has offered a mitigation grant program in recent years, so it's worth checking what's available.
What buyers should know
Radon testing isn't part of a standard home inspection in BC, and a proper test takes three months, so it rarely fits inside a typical subject period. Here's how we usually suggest handling it:
- Ask the seller whether the home has been tested and whether a mitigation system is installed.
- Look for a radon fan and pipe in the basement or garage. It's a good sign, not a red flag.
- Plan to test after you move in, and budget for mitigation just in case.
- If you're building, ask your builder about a radon rough-in. It's much cheaper to add during construction.
What sellers should know
If you've tested, keep your results. If you've mitigated, keep the paperwork and a post-mitigation test. Buyers who are new to the Interior often ask, and having clear answers builds trust.
The bottom line
Radon isn't a reason to avoid the Kootenays. It's just part of being a smart homeowner here, like having good winter tires. Test once, fix it if you need to, and get on with enjoying your home.
Have questions about radon in a home you're buying or selling? We're happy to point you to local testing and mitigation resources. Connect with us here.
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