How to Interpret Your Radon Test Results

You got a number. Now what?

Radon test results come back as a number measured in becquerels per cubic metre (Bq/m³). If you're in the US or reading older Canadian materials, you might see the same measurement expressed in picocuries per litre (pCi/L). They're different units for the same thing — 1 pCi/L equals approximately 37 Bq/m³.

Here's how to read what you got.

The Canadian reference levels

Below 100 Bq/m³ — Low

Your home is in a good range. The World Health Organization's guideline is 100 Bq/m³ — so you're at or below the international threshold. No action is required. Health Canada recommends retesting every 2–5 years, since radon levels can shift with renovations, changes to ventilation, or seasonal variation.

100–200 Bq/m³ — Elevated

You're below Health Canada's action level but above the WHO guideline. This is a grey zone. You're not required to take action, but it's reasonable to either conduct a longer test to get a more accurate reading, or consult with a contractor about whether mitigation makes sense for your situation.

A short-term test in this range can be misleading. If your test was 48–96 hours, a long-term test (90+ days) will give you a more reliable picture before you make any decisions.

200–600 Bq/m³ — Action Level

You're at or above Health Canada's action level. Mitigation is recommended. This doesn't mean there's an emergency, but it does mean prolonged exposure at this level carries meaningful health risk. A certified contractor can assess your home and install a system — in most cases, levels can be brought well below 100 Bq/m³.

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

Above 600 Bq/m³ — High

Health Canada recommends taking action within one year. The sooner you mitigate, the better — radon exposure accumulates over time, and the health risk at this level is significant with prolonged exposure. This is not a reason to panic, but it is a reason to act promptly.

One number isn't the whole story

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

Long-term tests (90+ days) are more reliable because they average out these fluctuations. Health Canada recommends them for making decisions about mitigation. The best time to run a long-term test is during the heating season (October through April in most of Canada), when windows and doors are closed and radon concentrations tend to be highest.

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

Where you tested matters

Radon accumulates most heavily in the lowest parts of a home. Results vary significantly by floor.

Test in the lowest liveable area — typically a basement or main floor if you don't have a basement. If you tested in a second-floor bedroom, your result is likely lower than what's happening in the basement, which may understate your actual exposure.

If you've only tested on an upper floor, consider running a second test in the basement.

What to do based on your result

Below 100 Bq/m³: Retest in 2–5 years. No action needed now.

100–200 Bq/m³: Consider a long-term test if you only have a short-term result. 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. Mitigation is recommended. Most systems cost $1,500–$3,000 and are installed in a day.

600+ Bq/m³: Act within the year. Don't delay.

What mitigation actually does

A radon mitigation system — typically sub-slab depressurization — draws radon gas out from under your foundation and vents it outside before it can enter your home. A fan runs continuously (using roughly the energy of a light bulb) and the system requires minimal 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.

Tools to help

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

Not sure what step to take next? Try our Situation Assessment at radonfinder.ca/tools/radon-assessment — five questions, two minutes, tailored recommendation.