Glossary · Health & indoor air
Radon mitigation (sub-slab depressurization)
Also called: radon reduction · radon remediation · active soil depressurization · sub-slab suction · radon fan · radon mitigation system
Fixing high radon, usually with a pipe through the basement floor and a fan that pulls soil gas from under the slab and vents it outside.
What it means
Sub-slab depressurization makes the pressure under the floor lower than in the house, so soil gas is drawn into the pipe instead of indoors. Sealing cracks and sumps helps but isn't enough on its own, and an HRV gives only modest reductions. The fan runs continuously, and a follow-up test confirms the fix.
Why it matters in an audit
Mitigation is usually affordable and very effective, and it's easiest to plan alongside basement air sealing or renovations.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| Effectiveness | Health Canada: most homes can be reduced by more than 80%; EPA: sub-slab suction cuts levels 50%–99% | epa.gov ↗ |
| Exhaust placement (EPA) | Vent above the roof and at least 10 feet above the ground | epa.gov ↗ |
| Testing afterwards, US | Within 30 days of installation but not sooner than 24 hours, using a 2–7 day test; retest at least every 2 years | epa.gov ↗ |
In the United States
EPA suggests checking with your state radon office for licensed or certified contractors and getting an independent follow-up test.