You can test for radon at any time of year. Health Canada recommends the heating season (October-April) for the most representative results, but a test done in any season is better than no test at all.
If you're wondering when to test for radon in Canada, the short answer is: the best time to start is now. If you can begin between October and January, you'll capture the strongest long-term heating-season window. But if you're thinking about testing in spring or summer, it's still worth doing.
Why October to April Is the Ideal Testing Window
Health Canada recommends testing for radon during the heating season, which runs roughly from October through April in most of Canada. During these months:
- Windows and doors stay closed — reducing natural ventilation that dilutes indoor radon
- Heating systems create negative pressure — the stack effect draws soil gases (including radon) into the home through foundation cracks and gaps
- Indoor radon levels are typically at their highest — giving you a reading that reflects the period when indoor radon levels are typically highest
Testing during the heating season captures the period when you're most exposed, making your long-term average more representative of your actual risk.
Why 91+ Days Matters More Than the Start Date
The duration of your test matters more than the exact start date. Health Canada recommends long-term testing of at least 3 months as the most reliable way to measure your home's radon level. Short-term tests (2–7 days) can vary dramatically depending on weather, wind, and barometric pressure.
A 91-day alpha-track test — the type included in every RadonTest.ca kit — accounts for these daily fluctuations and gives you a dependable average. Our lab partner, Lex Scientific, analyses alpha-track detectors, which are designed for reliable long-term measurement.
Can You Test in Summer?
Yes, you can test at any time of year. However, summer testing has limitations:
- Open windows and increased ventilation mean indoor radon levels are typically lower in summer
- A summer-only test may underestimate your actual annual exposure
- If your summer result is already above 200 Bq/m³, your heating-season levels are likely even higher
If you start testing in spring or summer, your result is still valuable — especially if it overlaps with part of the heating season. A test that spans May through August will give a lower reading than one from November through February, but it's still better than not testing at all.
The Best Time to Order Your Kit
To capture the full heating season with a 91-day test, the ideal order windows are:
- September–October: Kit arrives in early fall, test runs through winter. This captures the peak heating season and gives you results before spring.
- November–January: Still captures the core of heating season. Results arrive in spring.
- February–March: Latest recommended start for a heating-season test. Results arrive in late spring/early summer.
At RadonTest.ca, we send 10 email reminders over the 91-day period so you never forget about your test. Whether you start in October or January, we'll keep you on track from placement to results.
How Often Should You Retest?
Health Canada recommends retesting your home:
- Every 5 years as a routine check
- After major renovations that affect the foundation, basement, or ventilation system
- After installing a radon mitigation system to confirm it's working
- If you move to a new home — every home is different, even on the same street
Don't Wait for Perfect Timing
The worst time to test for radon is never. If it's June and you're thinking about it, order a kit. Your result may be slightly lower than a winter reading, but you'll still know whether your home's radon level is above the Health Canada guideline of 200 Bq/m³ — and that knowledge is worth having regardless of the season.
Ready to start? Order your RadonTest.ca kit — it includes the detector, prepaid return shipping, lab analysis, and results delivered with clear Health Canada context. See our FAQ for more details.