Short answer
Compare your long-term average to Health Canada’s guideline of 200 Bq/m³. Below 200 needs no action. Between 200 and 600, reduce radon within two years; above 600, within one year. If your result is in pCi/L, multiply by 37 to get Bq/m³ (4 pCi/L ≈ 148 Bq/m³). Short-term results are screening only and should be confirmed with a 91-day test.
Key facts
- Under 200 Bq/m³: below the Canadian guideline.
- 200–600 Bq/m³: reduce within 2 years. Over 600: within 1 year.
- 1 pCi/L = 37 Bq/m³.
- A short-term result is a screen, not a verdict.
Check your number
Enter a number to see what it means.
Health Canada’s guideline is 200 Bq/m³, based on a long-term test of at least three months.
Converting pCi/L and Bq/m³
Canadian labs report in becquerels per cubic metre (Bq/m³). Many U.S.-made kits and digital monitors report in picocuries per litre (pCi/L). The conversion is simple: 1 pCi/L = 37 Bq/m³.
| pCi/L | Bq/m³ | Meaning in Canada |
|---|---|---|
| 2.7 | 100 | WHO reference level |
| 4.0 | 148 | U.S. EPA action level (below Canada’s guideline) |
| 5.4 | 200 | Health Canada guideline |
| 8.1 | 300 | Reduce within 2 years |
| 16.2 | 600 | Reduce within 1 year above this |
Long-term results: what to do
A long-term result (at least 91 days) is what Health Canada’s guideline is built on. If yours is above 200 Bq/m³, plan to reduce it: within two years for 200–600 Bq/m³, within one year above 600. You don’t need a second long-term test to confirm a long-term result before mitigating.
Short-term and digital monitor results
Readings from tests of a few days, or a few weeks on a digital monitor, can be well above or below the yearly average. Use them as a screen:
- Well below 200: encouraging, but confirm with a long-term test during the heating season.
- Around or above 200: run a long-term test to confirm before spending money on mitigation.
- Several hundred or higher: start a long-term test now and talk to a mitigation professional. It’s reasonable to book an assessment in parallel.
A short reading is most trustworthy when it’s far from 200 and taken in winter. That’s the idea behind our 2-week early reading: a professional monitor runs alongside your long-term detector, so you get a likely answer early and the full answer at 91 days.
In a real estate transaction, there often isn’t time for a long-term test. See radon when buying or selling for practical options.
If you tested more than one room
Health Canada’s guideline applies to each normal occupancy area. If one detector is above 200 and another below, act on the higher result for that part of the home. A mitigation system treats the whole slab, not just one room.
After mitigation
A properly designed sub-slab system typically cuts radon by 90% or more. Confirm with a follow-up test: a short check soon after installation, then a long-term test through the next heating season. Re-test every few years and after major renovations, changes to the foundation, or changes to heating and ventilation.
Common questions
Is 4 pCi/L high in Canada?
4 pCi/L is about 148 Bq/m³: the U.S. EPA action level, but below Health Canada’s 200 Bq/m³ guideline. Under Canadian guidance no action is required, though some families choose to reduce it.
My digital monitor shows a big spike. Should I worry?
Short spikes are normal; radon changes hour to hour with weather and how the house is used. Look at the long-term average, ideally over 91 days or more, before deciding.
My result was 210 Bq/m³. Is that really a problem?
It’s just above the guideline. Health Canada recommends reducing it within two years. Mitigation would typically bring it well below 100 Bq/m³, and costs the same whether you start at 210 or 410.