4-day or 91-day radon test which one decides
Radon moves with weather, wind, and how closed the house is. A few days can land high or low compared with the winter average. Health Canada treats at least three months as the reading to compare with 200 Bq/m³.
Use 4 days when
You need a first number this week: a room you are about to sleep in, or a sale that will not wait three months. Treat a high 4-day result as a reason to follow with 91 days, or to act if the closing date will not allow it.
Use 91 days when
You live in the house and you want the number that decides mitigation. Place it in the heating season. Where it sits.
The 4-day test is a first reading. The 91-day test is the length Health Canada uses to judge a full heating season. Both are $59 before tax. Shipping, the prepaid return, and the lab are included. Tax is extra. The PDF report is emailed within 2 business days after the lab receives the detector.
Above 200 Bq/m³, the fix is a fan that pulls soil gas from under the slab and exhausts it above the roof. Radon Gas is C-NRPP certified for testing and for mitigation, and ships kits across Canada. Start from the Canada test page.
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