91-day radon detector — Health Canada method

This radon detector measures for 91 days (about 3 months). It is the format Health Canada recommends to estimate annual exposure, especially during the heating season.

91-day radon detector — Health Canada method

A C-NRPP / PNCR-C certified measurement over 91 days. Radon changes with the weather, ventilation and heating. A 91-day average is more representative than a 4-day screen. Use this test when you want to know if mitigation is actually needed.

When to use the 91-day test

• You live in the home and can leave the detector in place for 3 months
• You want the measurement Health Canada describes for annual exposure
• Winter / heating season, when the house is closed

Need a result before a closing? Use the 4-day detector as a screen, then confirm with 91 days if you stay in the house.

How it works

1. Place the detector in the lowest lived-in room, at breathing height, away from doors, windows and heat sources.
2. Leave it in place for 91 days.
3. Send it back in the prepaid envelope.
4. Receive the report by email, usually within 24 hours of arrival at the lab. We call you if the result is above 200 Bq/m³.

Health Canada guideline: 200 Bq/m³. Above that, mitigation is recommended. The test measures the level; it does not remove radon.

Compare 4-day and 91-day tests · Ships across Canada.