You placed your alpha track detector, waited the recommended 90 days (or longer), mailed it to the lab — and now you have results. A number in Bq/m³, a lab report, maybe a recommendation. What does it all mean, and what should you do next?
This guide walks you through exactly how to interpret your radon test results and what actions to take based on what you find.
Understanding the Number
Your radon test result is expressed in becquerels per cubic metre (Bq/m³). One becquerel equals one radioactive decay event per second. The higher the number, the more radon was present in your home during the test period.
Here's how to interpret your result:
| Result | Interpretation | Next Step |
|---|---|---|
| Below 100 Bq/m³ | Low — below WHO reference level | No action required. Retest in 2–5 years. |
| 100–199 Bq/m³ | Moderate — above WHO level, below Health Canada action level | Consider mitigation, especially in living spaces below grade. |
| 200–599 Bq/m³ | Elevated — above Health Canada's 200 Bq/m³ action level | Mitigate within one year. |
| 600–999 Bq/m³ | High | Mitigate within a few months. |
| 1,000+ Bq/m³ | Very High | Act immediately. Limit time in affected areas until mitigated. |
Is Your Test Result Accurate?
A long-term alpha track test (90+ days) is the most accurate residential radon measurement method available. It accounts for seasonal variation — radon levels fluctuate with temperature, barometric pressure, soil moisture, and ventilation habits — and produces a reliable annual average estimate.
To ensure your result is valid, the detector must have been:
- Placed in the lowest occupied level of the home (finished basement, or main floor if no basement)
- Left undisturbed for the full test period with normal living conditions
- Not placed near windows, doors, HVAC vents, or exterior walls
- Kept at least 50 cm from the floor and 50 cm from any wall, away from direct sunlight
- Mailed back within the expiry timeframe shown on the detector packaging
If any of these conditions were significantly violated, the result may not accurately represent your home's average radon level. Contact your lab — most will advise on whether a re-test is warranted.
What Does "Annual Average Estimate" Mean?
Labs typically convert your test-period average to an estimated annual average using a seasonal correction factor. This accounts for the fact that radon levels are generally higher in winter (when homes are sealed) than in summer. If you tested only in winter, the correction will adjust your result downward to reflect a more accurate full-year average.
The reported number is your best estimate of long-term exposure — use it as your decision-making baseline.
My Result Is Above 200 Bq/m³ — What Now?
First: don't panic. Radon mitigation is reliable, cost-effective, and widely available across Canada. A properly installed sub-slab depressurization (SSD) system will reduce your radon level by 80–99% in most homes.
Your options:
- Hire a C-NRPP certified mitigator. Search the C-NRPP directory for a certified professional in your area. A professional installation typically costs $1,500–$3,000 and includes a post-mitigation test.
- DIY mitigation. If you're handy, a sub-slab depressurization system is an achievable weekend project. You'll need a radon fan, PVC pipe, a pipe seal or sump dome, and a manometer for system verification. Browse our radon fan collection and fan selection guide.
After mitigation, re-test your home with a new long-term detector to confirm the system is working effectively. Most successful mitigations bring levels below 100 Bq/m³.
My Result Is Between 100–200 Bq/m³ — Should I Mitigate?
This is the most common question we receive. Health Canada's official guidance is that you should consider mitigation at this range. Our recommendation: yes, mitigate.
Here's why: the cost of a mitigation system is modest (a fan runs $280–$580, plus installation materials), and it will likely bring your level below 50 Bq/m³. The risk reduction is real and permanent. There is no downside to having a lower radon level.
My Result Is Below 100 Bq/m³ — Am I Done?
You don't need to take immediate action, but radon levels change over time. We recommend retesting every 2–5 years, or after any of the following events:
- Major renovations (especially basement finishing or foundation work)
- Changes to your HVAC system
- Buying or selling the home
- Significant changes to how lower levels of the home are used
Keep Your Test Results
Store your lab report somewhere permanent. It's valuable documentation for future real estate transactions, insurance purposes, and as a baseline for future tests. Take a photo and save it to cloud storage.
Ready to test? Our Radtrak³ Long Term Alpha Track Test Kit is analyzed by an accredited radon laboratory — the same detector used by home inspectors and C-NRPP professionals across Canada. Return it using the included pre-addressed mailer and access your results online.
