Dosimeter or monitor the 91-day average is what the guideline uses
The 91-day detector — an alpha track or another long-term device — stays in place, then the laboratory calculates an average. That is the form Health Canada compares with the guideline. The 4-day test is a short reading for a deadline. A continuous monitor shows points every hour: useful for seeing the night, a stopped fan, or the effect of a window.
Looking at the screen on a Tuesday evening and deciding “it’s fine” misses the other 90 days. Leaving a monitor for a year is another strategy, if you know which average the device calculates and which room it is in. 4 days or 91 days. A 2-hour test.
Reference points: Health Canada, what you need to know about radon and the 200 Bq/m³ guideline. The two-year timeline between 200 and 600, and one year above 600, comes from Health Canada’s guide for radon measurements in homes.
The 4-day test gives a first reading. The 91-day test covers the three-month minimum Health Canada asks for. Both are $59 before tax: shipping, return and the laboratory are included, taxes extra. The PDF report is sent within 2 business days after the laboratory receives the detector.
Above 200 Bq/m³, mitigation is confirmed with a quote. Gaz Radon is C-NRPP certified for measurement and mitigation.
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