How to Interpret Your Radon Test Results

Your result came back as a number in becquerels per cubic metre (Bq/m³). If you're looking at an older Canadian document or a US-sourced test, you might see pCi/L instead. They measure the same thing: 1 pCi/L equals roughly 37 Bq/m³.

Here's how to read what you got.

The Canadian reference levels

Below 100 Bq/m³

You're in good shape. The WHO's guideline is 100 Bq/m³, so you're at or below the international threshold. No action needed. Health Canada recommends retesting every 2–5 years since radon can shift after renovations or changes to ventilation.

100–200 Bq/m³

You're below Health Canada's action level but above the WHO guideline. This is a grey zone. You're not required to act, but it's reasonable to run a longer test if you only have a short-term result, or to talk to a contractor about whether mitigation makes sense for your situation.

200–600 Bq/m³

You're at or above Health Canada's action level. Mitigation is recommended. This isn't a health emergency, but prolonged exposure at this level carries real risk. A certified contractor can assess your home and install a system. In most cases, levels come down well below 100 Bq/m³.

Health Canada recommends acting within two years at 200–600 Bq/m³.

Above 600 Bq/m³

Act within the year. Radon exposure accumulates, and the health risk at this concentration is serious with prolonged exposure. This is not a reason to panic. Get quotes from certified contractors and schedule the work.

One number isn't the whole story

Radon fluctuates by time of day, season, weather, and how you're using your home. A single test gives you a snapshot, not a complete picture.

Long-term tests (90+ days) are more reliable because they average out those swings. Health Canada recommends them for mitigation decisions. Run one during heating season (October through April in most of Canada) when your home is sealed and radon concentrations are at their highest.

Short-term tests (48–96 hours) are faster but less accurate. They're often used in real estate transactions where time is short. If a short-term result is your only data point and it's somewhere between 150 and 250, run a long-term test before committing to mitigation.

Where you tested matters

Radon builds up in the lowest parts of a home. A test on the second floor will almost certainly read lower than a test in the basement. That can understate your actual exposure.

Test in the lowest livable area, typically the basement or main floor if there's no basement. If you've only tested upstairs, consider running a second test lower down.

What to do with your result

Below 100 Bq/m³: Retest in 2–5 years. You're done for now.

100–200 Bq/m³: If you only have a short-term result, do a long-term follow-up. Consult a contractor if you're concerned. Some homeowners in this range choose to mitigate; others wait and retest.

200+ Bq/m³: Get a quote from a certified contractor. Most systems cost $1,500–$3,000 and go in within a day.

600+ Bq/m³: Don't delay. Schedule mitigation this season.

What mitigation actually does

A radon mitigation system, typically sub-slab depressurization, draws gas from under your foundation and vents it outside before it can get into your home. A fan runs continuously using roughly the energy of a light bulb, and the system needs very little maintenance.

A well-installed system brings most homes well below 100 Bq/m³. Post-installation testing, done after the system has been running for at least 24 hours, confirms it's working.

Helpful tools

Use our Radon Result Interpreter at radonfinder.ca/tools/understand-your-results to convert between Bq/m³ and pCi/L and get a plain-English read on your number.

Not sure what step to take next? Try our Situation Assessment at radonfinder.ca/tools/radon-assessment. Five questions, two minutes, and you'll get a clear recommendation.