A note before you read. This article is general information for Canadian homeowners — not medical, legal, financial, or warranty advice. Radon results are reported against Health Canada's guideline of 200 Bq/m³. RadonTest.ca coordinates kit logistics and sample submission only; we do not interpret your results or assess your health. All analysis is performed independently by a C-NRPP-certified laboratory.
Quick answer
A radon map can tell you the odds for your region — it can never tell you the level inside your specific home. Area data is built from many individual test results and the local geology, so it shows where elevated radon is more common or less common. But two houses on the same street can test very differently because radon depends on that home's soil, foundation, construction and air-tightness. Treat a map as a starting point, then run a long-term test — the only way to actually know your home's number.
What a radon map actually shows
Radon comes from the natural breakdown of uranium in soil and rock. Because geology varies across the country, so does the tendency for radon to build up indoors. A radon map takes thousands of individual home-test results, plus what is known about the ground beneath a region, and turns them into a picture of prevalence: the share of tested homes in an area that came back above Health Canada's 200 Bq/m³ guideline.
That is genuinely useful information. It helps public-health agencies decide where to focus awareness campaigns, and it helps you understand the general radon "climate" where you live. Health Canada's own material on radon levels in Canada, and the province-by-province summaries published by programs such as Take Action on Radon, are built the same way.
What a map is not is a reading of your house. A prevalence figure is an average across many different buildings, each with its own foundation, age and ventilation. Averages describe crowds, not individuals. If you want the regional picture for your own area, look it up on the RadonTest.ca Radon Map and read our companion piece on radon levels by province — then keep reading here for why that picture stops at your property line.
Why your neighbour's result can't predict yours
It is common for two homes a few metres apart to return very different results — one comfortably below the guideline, the other well above it. That surprises people, but it makes sense once you see what actually drives the number inside a house. Radon entry is a combination of how much gas is in the ground, how easily it can get in, and how much it can accumulate before it is diluted by fresh air.
| Factor | Why it changes a home's radon level |
|---|---|
| Soil and bedrock directly under the home | Local pockets of uranium-bearing rock and soil permeability differ over very short distances. |
| Foundation type and condition | Cracks, gaps around pipes, a sump pit, or a crawl space give soil gas a path indoors. |
| Age and construction methods | Slab detailing, sub-slab material and sealing all affect how much gas enters. |
| Air-tightness, HVAC and ventilation | A tighter, more energy-efficient home can hold radon in; ventilation can dilute it. |
| How the home is lived in | Basement use, how often windows are opened, and heating patterns move the number up or down. |
| Weather and season | Cold weather and the "stack effect" tend to draw more soil gas indoors during winter. |
Two neighbours can share the same soil map colour and still test on opposite sides of 200 Bq/m³ because their foundations, renovations and daily habits are not the same. This is also why you can't rely on a friend's result, a previous owner's word, or a builder's reassurance. For more myths like this, see our roundup of common radon misconceptions.
"Higher-prevalence" and "lower-prevalence" — and why the label doesn't decide it
You will notice we don't call any area "risk-free" or "dangerous." Those words don't fit how radon behaves. Instead, it's more accurate to think in terms of higher-prevalence regions (where a larger share of tested homes came back above the guideline) and lower-prevalence regions (where fewer did). That framing keeps the focus where it belongs: on odds, not certainties.
Here's the part homeowners most often get wrong. In a lower-prevalence region, individual homes still test above 200 Bq/m³ — just fewer of them, proportionally. And in a higher-prevalence region, plenty of homes test below the guideline. A map can shift the probability, but it can't rule your house in or out. That's precisely why Health Canada recommends that every home be tested, regardless of where it sits on any map. You can read more about how the guideline is meant to be used in our guide to acceptable radon levels in Canada.
It's also worth being clear about what a result below 200 does and doesn't mean. A reading under the guideline means no action is recommended at this time — it does not mean the air is "radon-free," and it does not mean the number will stay the same forever after a renovation, a foundation change, or years of settling. Radon is a health risk that scales with exposure over time, which is why it remains the leading cause of lung cancer among people who have never smoked. If you want the health context, see is radon dangerous?
How to use a radon map the right way
A map is a great first step when you use it for what it's good at. Here's a sensible order of operations:
- Look up your area. Start with the RadonTest.ca Radon Map to see the general prevalence where you live, and cross-reference the provincial data.
- Read it as context, not a verdict. A higher-prevalence area is a nudge to test sooner; a lower-prevalence area is not a reason to skip testing.
- Note what the map can't see. It doesn't know your foundation, your renovations, or how you run your home in January.
- Test your own home. This is the only step that produces a number that's actually about your house.
Think of the map like a weather forecast for your region and the test like stepping outside to check the temperature at your own front door. The forecast is helpful; it's still not the reading you act on.
The only way to know your home is to test it
Health Canada and the Canadian Cancer Society agree on the bottom line: the only way to know your home's radon level is to measure it. The recommended method is a long-term test using an alpha-track detector left in place for at least 91 days. A longer measurement averages out the day-to-day and weather-driven swings that a short "snapshot" test can't capture.
The heating season (roughly late fall through winter) is still the ideal window because homes are closed up and radon tends to be highest. That said, updated Health Canada guidance now allows testing at any time of year — so the best time to start is genuinely whenever you're ready, rather than waiting months for "perfect" conditions. For the full method, see our summary of Health Canada's testing guidance.
Placement matters, too: a long-term detector should sit in the lowest lived-in level of the home, away from drafts, exterior walls and high humidity. Our guide on where to place a radon test kit walks through it. When your results come back, they'll be reported against the 200 Bq/m³ guideline. If your reading is at or above it, don't panic — radon is one of the more fixable issues a home can have, and our article on what to do if your radon level is above 200 explains the next steps.
FAQ
Does a radon map tell me whether my house has radon? No. A map shows regional prevalence built from aggregated test results and geology. Your home's level depends on its own soil, foundation, construction and air-tightness, so only a test of your home can tell you your number.
My area looks lower-prevalence on the map — can I skip testing? No. Even in lower-prevalence regions, individual homes test above 200 Bq/m³. Health Canada recommends that every home be tested regardless of where it falls on a map.
Two houses on my street tested very differently. How is that possible? Differences in foundation type and condition, cracks or a sump, sub-slab soil, ventilation, and how each home is heated and lived in can push two nearby homes to opposite sides of the guideline.
What counts as a "high-radon area"? There's no official "high" or "risk-free" label. We use higher-prevalence to describe regions where a larger share of tested homes exceeded the guideline. It reflects odds for the area, not a guarantee about any single home.
Where can I look up my area? Start with the RadonTest.ca Radon Map and provincial data, then treat that as background. The map is the starting point; a long-term test of your home is the answer.
How long does a proper test take? The recommended test is a long-term alpha-track measurement of at least 91 days. Updated Health Canada guidance allows testing at any time of year, though the heating season remains ideal.
Is any area considered radon-risk-free? No area is labelled "risk-free." Radon varies home by home, and a result below 200 Bq/m³ means no action is recommended — not that a home is radon-free. Testing is the only way to know your level.
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Sources
- Health Canada — Radon: https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon.html
- Health Canada — About radon (radon levels in Canada): https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/about.html
- Health Canada — Testing your home: https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/testing-your-home.html
- Take Action on Radon — What's happening in your province: https://takeactiononradon.ca/provinces/
- C-NRPP — Find a professional: https://c-nrpp.ca/find-a-professional/
- Canadian Cancer Society — Radon: https://cancer.ca/en/cancer-information/reduce-your-risk/know-your-environment/radon
Ready to find out what your home actually reads?
A map can only tell you the odds for your area — it stops at your property line. To learn your home's number, order the RadonTest.ca radon test kit. It's all-inclusive: a C-NRPP-listed long-term detector, tracked shipping both ways, analysis by a Canadian C-NRPP-certified laboratory, and your official Certificate of Analysis reported against Health Canada's 200 Bq/m³ guideline. Look up your region on the Radon Map, then get your kit and test your home.
RadonTest.ca does not diagnose, treat, or prevent disease, and is not affiliated with Health Canada or C-NRPP.