A note before you read. This article is general information for Canadian homeowners — not medical, legal, or financial 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, and we do not perform mitigation work. All analysis is performed independently by a C-NRPP-certified laboratory.
Quick answer
Radon can typically be reduced by more than 80%, usually in less than a day, for about the cost of other common home repairs. The method that does the work in nearly every Canadian home is sub-slab depressurization — a sealed pipe and a fan that draw soil gas out from beneath the floor before it can enter, installed by a C-NRPP-certified professional.
Before any of that, you need a number: a long-term test of at least 91 days. Mitigation decisions are made on that, not on a short test or a neighbour's result.
This page is the map. Each step links to the article that goes deep on it.
Step 1 — Confirm you actually have a number to act on
The guideline is 200 Bq/m³ as an annual average, and Health Canada is explicit that short-term tests are "not appropriate for informing mitigation decisions". So the starting point is a 91+ day result from the lowest lived-in level.
What that result means:
| Long-term result | What Health Canada guidance suggests |
|---|---|
| Below 200 Bq/m³ | No action recommended. Lower is still better — no level is risk-free. |
| 200–600 Bq/m³ | Reduce the level within one year. |
| Above 600 Bq/m³ | Reduce the level within one year — the higher the level, the sooner you should act. |
Acceptable radon levels in Canada goes through the bands in more detail.
Step 2 — Understand what actually removes radon
The thing that works is active sub-slab depressurization. A pipe is sealed into the floor slab, and a continuously running fan keeps the space beneath the slab at slightly lower pressure than the house. Soil gas takes the easy route out through the pipe instead of finding its way in through cracks.
That is the whole idea, and it is why it is so effective: it deals with radon before it enters, rather than trying to clean it up afterwards.
How radon mitigation works explains the system in full.
Step 3 — Know what doesn't work on its own
This is where a lot of money gets wasted:
- Sealing cracks alone. Worth doing as part of a system, but on its own it rarely produces a meaningful reduction — radon finds the next opening.
- Air purifiers and HEPA filters. They capture particles. Radon is a gas.
- Houseplants. No effect at the concentrations involved.
- Opening windows. Helps while they are open, in a Canadian winter that is not a plan, and it does nothing for the annual average.
- Ventilation upgrades (HRV/ERV). Can dilute radon somewhat and are good for air quality generally, but they are not a reliable route from above the guideline to below it.
Step 4 — Decide who does the work
Health Canada's recommendation for a result above the guideline is to hire a C-NRPP-certified radon mitigation professional. There is a real reason beyond credentials: system design depends on your foundation, your soil and your house's pressure behaviour, and getting the suction point or fan sizing wrong produces a system that runs, costs money, and does not fix the problem.
The DIY question comes up often enough that it has its own article — DIY radon mitigation in Canada covers what a homeowner can reasonably do and where the line is. When you are ready to hire, how to choose a radon mitigator covers what to ask for, and what mitigation costs in Canada sets expectations on price.
Step 5 — Confirm it worked, and keep confirming
A mitigation system is not finished when it is installed — it is finished when testing shows the level has come down. Health Canada's post-mitigation sequence has three parts:
- A short-term test started at least 24 hours after the fan is turned on, ideally in the same location where the original measurements were made. Health Canada recommends a C-NRPP-certified professional carry this out, to demonstrate the system is working.
- A long-term test of at least three months during the following fall or winter, to confirm the annual average has come down below the guideline. This is the one that closes the file.
- A retest every five years thereafter for homes with active mitigation systems, because fans age and conditions change.
Health Canada is also explicit about who should not do that testing. From the Radon — Reduction Guide for Canadians: “To avoid conflict of interest, the test should not be performed by the company that installed the radon mitigation system.” If the company that installed your system offers to verify its own work, have the measurement done by someone else.
That five-year interval applies specifically to mitigated homes. There is no blanket "retest every X years" rule for every house, and no such thing as a result that expires.
FAQ
How do you get rid of radon in a house? With active sub-slab depressurization: a sealed pipe through the floor and a continuously running fan that draws soil gas out from under the slab before it enters. Installed by a C-NRPP-certified professional, it typically reduces levels by more than 80%.
Can you remove radon completely? No, and that is not the goal. Radon is naturally present everywhere; mitigation brings the concentration down, typically well below the guideline, rather than eliminating the gas.
Will sealing cracks fix a radon problem? Not by itself. Sealing supports a mitigation system by reducing competing openings, but on its own it seldom achieves a meaningful reduction because the gas finds other routes.
Do air purifiers remove radon? No. Filters and purifiers are designed to capture particles; radon is a gas and passes straight through.
How long does radon mitigation take? Health Canada notes a system can usually be installed in less than a day, for about the same cost as other common home repairs.
How do I know the system is working? Retest with a long-term test after installation, and retest every five years thereafter, which is Health Canada's recommendation for homes with active mitigation systems.
Does opening windows reduce radon? Only while they are open, and it does nothing meaningful for the annual average the guideline is based on — which makes it unworkable as a Canadian winter strategy.
Sources
- Health Canada — Reducing radon levels in your home: https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/reducing-levels-home.html
- Health Canada — Radon reduction guide for Canadians: https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/radon-reduction-guide-canadians-health-canada.html
- Health Canada — Government of Canada radon guideline: https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/government-canada-radon-guideline.html
- Canadian National Radon Proficiency Program (C-NRPP) — Find a professional: https://c-nrpp.ca/find-a-professional/
Start with the number
Mitigation decisions are made on a long-term result, so that is the first step. Our kit includes the C-NRPP-listed detector, prepaid analysis at a C-NRPP-certified Canadian laboratory, return shipping and your Certificate of Analysis — and the reminders that get it finished on time.