Radon in a crawl space test the room above, fix the soil path
A crawl space with bare soil or gravel is an open path for soil gas. In winter the vents are often closed and the house draws air upward, so some of that gas reaches the rooms. A plastic sheet on the ground that is not sealed to the walls slows moisture more than it stops radon.
Health Canada’s 200 Bq/m³ guideline is for a normally occupied area. Put the detector in the lowest room people use, not only in the middle of a crawl space nobody enters. A number from an empty space is not the exposure.
What the fix looks like
Mitigation suctions under the membrane or from a low point and exhausts above the roof. It is not a bathroom fan and not an HRV left on a guess. How the system works. Does an HRV lower radon?
After the work
Retest the same occupied room for 91 days in the heating season. After mitigation.
The 4-day test is a first reading. The 91-day test is the length Health Canada uses to judge a 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. Gaz Radon is C-NRPP certified for testing and for mitigation, and ships kits across Canada. Start from the Canada test page.
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