When you should mitigate
Health Canada recommends action based on how high your long-term test result is:
- Above 600 Bq/m³ — mitigate within one year.
- 200–600 Bq/m³ — mitigate within two years.
- 100–200 Bq/m³ — below the Canadian action line, but the WHO recommends reducing where practical.
How active sub-slab depressurisation works
The standard Canadian mitigation system is active sub-slab depressurisation (ASD). A contractor cores a hole through your basement slab, inserts a 3- or 4-inch PVC pipe, and routes it up through the house — usually inside a wall or a closet — and out above the roofline. An inline radon fan creates negative pressure beneath the slab, capturing radon gas before it can rise into your living space and venting it safely outside. Well-designed ASD systems reduce indoor radon by 80–99% and run for about the same power cost as a desktop computer.
For homes with crawl spaces, mitigators install a sealed polyethylene membrane and depressurise the space underneath. Homes built on engineered slabs or with multiple foundation sections may need more than one suction point.
What it costs in Canada
A typical single-family Canadian home costs $2,000–$3,500 for a complete ASD installation including the fan, manometer, sealing, and post-mitigation test. Complex foundations, finished basements that require careful routing, or homes needing multiple suction points can run $4,000–$6,000. Some provinces and municipalities offer rebates — check your provincial environment or health department before you book the install.
How to find a qualified contractor
Hire a mitigator certified by the Canadian National Radon Proficiency Program (C-NRPP). C-NRPP professionals follow Health Canada's mitigation standard, are insured, and warranty their work. You can search the C-NRPP directory online and most certified contractors will quote based on a site visit and your long-term test result.
Verify the system worked
Retest within 30 days of installation to confirm levels are below 200 Bq/m³, then again with a long-term test (or an ongoing real-time monitor) to make sure the system holds up year-round. See our testing guide for the right approach. The system fan should run continuously — switching it off lets radon return within hours.
Can I do it myself?
We do not recommend DIY mitigation. Improper suction-point placement, undersized fans, or unsealed sumps can leave radon levels unchanged or even pull soil gas into living areas. A certified C-NRPP installation includes diagnostic testing, proper venting above the roofline, and a post-install confirmation test that DIY work rarely matches.
Frequently asked questions
How much does radon mitigation cost in Canada?
A typical active sub-slab depressurisation system costs $2,000–$3,500 installed in most Canadian homes. Complex foundations, crawl spaces, or multiple slabs can push the cost to $5,000 or more.
What is the most effective radon mitigation system?
Active sub-slab depressurisation (ASD) is the standard. A fan pulls radon-laden air from beneath the slab and vents it above the roofline before it can enter the home. Properly designed systems routinely reduce indoor levels by 80–99%.
Will sealing cracks alone reduce radon?
No. Sealing cracks helps a depressurisation system work better, but on its own it rarely brings levels below the Health Canada guideline of 200 Bq/m³.
How do I find a radon mitigation contractor?
Use a contractor certified by the Canadian National Radon Proficiency Program (C-NRPP). Certified mitigators follow Health Canada's installation standard and warranty their work.
How long does mitigation take?
Most ASD installations are completed in one day. You should retest within 30 days to confirm the system brought levels below 200 Bq/m³.
Keep learning
Test before mitigating — and retest after to confirm the system worked.
When 200 Bq/m³ means action and 600 Bq/m³ means urgent action.
The health stakes that make mitigation worthwhile.
How your area compares before you invest in a system.