What does my radon test result mean?

Check your result

Your result Unit Bq/m³pCi/L Type of test Long-term test (91 days or more) Short-term test (under 91 days) Digital monitor, long-term average Digital monitor, a single reading Check result

How does the checker read a result?

In three steps. It converts the number to Bq/m³ if you entered pCi/L, using the fixed factor of 37. It compares the converted value with the three published reference levels. Then it looks at the type of test, because the same number means different things depending on how it was obtained.

The only official threshold in Canada is Health Canada's guideline of 200 Bq/m³ as an annual averagesource, and its guidance above that level is to reduce radon within a year, sooner when the result is highersource. The other bands are our own way of sorting results so the advice is easier to follow. The 100 Bq/m³ line comes from the World Health Organization's reference levelsource and the 148 Bq/m³ line from the US EPA's action level of 4 pCi/Lsource.

Why does the type of test matter?

Because the guideline is about an average over months, and not every number is one. Health Canada recommends measuring for three to twelve months, with 91 days as the minimumsource, and does not recommend testing for shorter periodssource. Radon moves with the weather, the season and the way a house is heated, so a few days can land well above or below the yearly figure.

• Long-term test: the result can be compared with the guideline directly.
• Short-term test: the checker shows where the number sits and asks you to confirm it with a long-term test, unless the reading is very high.
• Digital monitor, long-term average: a useful guide once the monitor has run for 91 days or more in the right room.
• Digital monitor, single reading: not comparable with the guideline. Wait for the long-term average.

C-NRPP tests consumer-grade electronic radon monitors and publishes the models it approves, notes that they cannot be professionally calibrated and are not approved for use by measurement professionals, and advises leaving them in place for at least three monthssource. That is why the checker treats a monitor's average as informative and a laboratory-analysed test as the record to keep.

What else should I check on my report?

Where the detector was, and when. Health Canada's guide places the detector in a room occupied for four hours a day or more on the lowest lived-in level, away from kitchens, bathrooms, vents and heat sourcessource. A reading from a furnace room, a cold storage room or a floor nobody uses does not describe what the household breathes, and a test that ran with the windows open through summer will usually read lower than the same home in winter.

The checker cannot see any of that. If your report leaves you unsure about the room, the dates or the device, send it with the form on this page. Those details change how a number should be read more often than people expect.

What should I do after checking?

It depends on which side of the guideline a long-term result falls.

• Under 200 Bq/m³: keep the report. Test again after renovations, and consider another winter test if the number is close to 200.
• Above 200 Bq/m³: plan mitigation within the year. Health Canada reports that a reduction system lowers radon by more than 80% in most homessource.
• Not a long-term result: run one, starting in the heating season.

Our pages on radon levels and the Canadian guideline, radon testing in Calgary and radon mitigation in Calgary cover each of those next steps, and the unit converter has a table of common values in both units.

Is the checker a substitute for advice?

No. It applies published reference levels to a number you supply. It does not know your house, it cannot tell whether a test was run properly, and it is not medical advice. What it can do is save you from the two most common misreadings: comparing a pCi/L number with a Bq/m³ guideline, and treating a few days of data as a yearly average.