A note before you read. This article is general information for Canadian homeowners and renters, drawn from publicly available Health Canada and Canadian National Radon Proficiency Program (C-NRPP) materials. It is not medical, legal, or warranty advice. Radon results are interpreted against the Health Canada guideline, and any decision to remediate should be based on a completed long-term test analysed by a qualified laboratory. RadonTest.ca coordinates kit logistics and sample submission only and does not provide medical advice or health assessments.
The short version: you can test your home for radon at any time of year. Health Canada still recommends a long-term test of at least three months, ideally during the heating season, for the most representative result — but its updated Guide for Radon Measurements in Homes (updated December 2025) makes clear how to act on a test taken outside that window. If your result is at or above the Health Canada guideline of 200 Bq/m³, you should take action to reduce it — no second test required. If your result is below the guideline but your test didn't capture enough of the heating season, Health Canada recommends a confirmatory re-test during the heating season. In other words: a high reading is always worth acting on, and a low reading is worth confirming in winter. Either way, the worst choice is to wait and do nothing.
What Health Canada actually recommends
Health Canada's position has two parts that are easy to confuse, so here they are plainly, as published in the Guide for Radon Measurements in Homes:
- Use a long-term test. Health Canada recommends measuring radon over a period of at least three months — and up to twelve — using a long-term detector such as an alpha-track or electret device. The minimum valid measurement period is 91 days. Short-term "snapshot" tests of a few days are not appropriate for deciding whether to mitigate.
- The heating season gives the most representative reading. Because homes are sealed and heating systems draw soil gas indoors, indoor radon is typically highest from roughly October to April. A test that includes at least 91 days of the heating season best reflects your home's true annual average.
Nothing about that has been weakened. What the updated guidance clarifies is the part homeowners ask about most: what a result means if you tested outside the ideal window.
The decision rule for off-season tests
Here is the practical logic, paraphrased from Health Canada's updated guide. (For the exact wording, read Health Canada's guide directly.)
If your long-term result is at or above 200 Bq/m³: Health Canada recommends taking corrective action to reduce the radon level — a re-test is not necessary to confirm a high result. Off-season readings tend to be lower than heating-season readings, so a result already above the guideline in, say, July strongly suggests your winter levels would be higher still. Acting on it is the right call.
If your long-term result is below 200 Bq/m³ but your test did not include at least 91 days of the heating season: Health Canada recommends re-testing so that at least 91 days fall within the heating season. A summer-weighted test can under-estimate your annual average, so a "below guideline" summer number is reassuring but worth confirming in winter.
This is why testing now — in any season — is genuinely useful. You either get an actionable high result you can move on immediately, or a low result you simply confirm during the next heating season. For a deeper walk-through of how readings are reported, see our guide on how to read your radon test results.
Why "wait until fall" is the costliest myth
The single most common reason Canadians give for not testing is timing — they intend to "wait for winter" and then forget. The updated guidance removes the excuse. Because a high off-season result is already actionable, there is no measurement reason to delay starting. And because a 91-day long-term test takes about three months to run plus lab turnaround, starting in late summer or early fall means your detector is already capturing the heating season as the weather turns.
If you'd like the detail on the seasonal science — open windows, the stack effect, and why winter readings run higher — see our companion article, When Is Radon Testing Season in Canada?
What the guideline number means
Health Canada's radon guideline is 200 Bq/m³ (becquerels per cubic metre) as an annual average in a normally occupied area of the home. Health Canada recommends that homes above the guideline be remediated, and advises acting sooner the higher the result — see Health Canada's guideline page for its recommended timeframes. Radon is the leading cause of lung cancer in Canada after smoking, and Health Canada estimates that radon is present in every home at some level, with a meaningful share of homes above the guideline. If your number comes back high, it is a solvable problem: see what to do if your radon level is above 200 Bq/m³.
Different organizations use different reference levels — the World Health Organization references 100 Bq/m³ and the U.S. EPA uses roughly 148 Bq/m³ — but in Canada the number that governs remediation guidance is Health Canada's 200 Bq/m³. We compare them in Radon guideline levels: Health Canada vs WHO vs US EPA.
Long-term test vs digital monitor
A continuous digital monitor can show you radon moving day to day, which is satisfying — but Health Canada is clear that mitigation decisions should rest on a long-term measurement, not a short-term snapshot. The practical approach for most homeowners is a long-term alpha-track test for the decision, with a monitor as an optional ongoing check afterward. We lay out the trade-offs in Long-term radon test vs continuous digital monitor.
How often to re-test
Health Canada recommends re-testing:
- Every five years as a routine check, and after any major renovation that affects the foundation, basement, or ventilation.
- After installing a mitigation system, to confirm it's working.
- When you move — every home is different, even on the same street.
- To confirm a below-guideline off-season result during the next heating season, as described above.
How RadonTest.ca fits in
Every RadonTest.ca kit uses a 91+ day alpha-track detector analysed in Canada by Lex Scientific, a C-NRPP-certified laboratory in Guelph, Ontario. Shipping is included both ways, your result is reported against the Health Canada guideline of 200 Bq/m³, and we send reminder emails across the testing window so the detector doesn't end up forgotten in a drawer. You can start any time of year — see exactly how it works.
Frequently asked questions
Can I test for radon in the summer? Yes. Health Canada recommends a long-term test of at least three months, ideally during the heating season, but you can test at any time of year. If a summer result is at or above 200 Bq/m³, Health Canada recommends taking action without re-testing. If it's below the guideline and your test didn't include at least 91 days of the heating season, re-test during the heating season to confirm.
Does Health Canada say I have to test only in winter? No. Health Canada identifies the heating season (roughly October–April) as giving the most representative reading, but its updated guide explains how to interpret tests taken in other seasons. The requirement is a long-term measurement of at least 91 days, not a specific start month.
Is a short-term (a few days) radon test good enough? No. Health Canada advises that short-term tests are not appropriate for deciding whether to mitigate. Use a long-term test of at least 91 days.
What is the Health Canada radon guideline? 200 Bq/m³ as an annual average in a normally occupied area of the home. Health Canada recommends remediating homes above the guideline, sooner the higher the level.
If my summer test is below 200, do I still need to retest? It's reassuring, but because off-season readings tend to run lower, Health Canada recommends confirming a below-guideline result with a test that includes at least 91 days of the heating season.
Ready to start? Order your RadonTest.ca kit — it includes the alpha-track detector, prepaid tracked return shipping both ways, certified Canadian lab analysis, and results delivered with clear Health Canada context. Questions first? See our FAQ.
Sources (all publicly available): Health Canada, Guide for Radon Measurements in Homes (updated December 2025); Health Canada, Radon guideline; Health Canada, Radon overview. This article does not reproduce any non-public material.