Intervention
Radon mitigation
Part of: Source control
Also: radon remediation, sub-slab depressurisation, radon sump, soil depressurisation, radon reduction
Building work that lowers indoor radon — most often by extracting soil gas from beneath the floor before it can enter, sometimes by sealing the entry paths or by changing how the building is ventilated. It is the one indoor measure with a legal duty behind it in many countries.
What it is
Radon enters a building because the air inside is at slightly lower pressure than the soil gas beneath it, so the ground is drawn in through cracks, service penetrations and the joint between floor and wall. Mitigation works on that pressure difference rather than on the gas.
The standard method reverses it: a fan draws air from a point under the floor slab and discharges it above the roof, so the soil gas goes up the pipe instead of into the house. Where it can be installed it is reliable and reductions are large. Sealing entry paths alone is weaker, because the pressure difference remains and finds another route. Ventilating the building dilutes what enters and also changes the pressure — which is why a system that extracts air without supplying it can make the problem worse.
Two consequences matter for the record: an installation must be verified by remeasurement, and a fan that stops working stops protecting.
What the studies report
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Radon | a single house, and the two measures were installed together, so the sub-slab depressurisation and the ventilation cannot be separated | — · home | mitigation study in a house: a decentralised mechanical ventilation system with heat recovery combined with a minimally invasive active sub-slab depressurisation, with radon, carbon dioxide and temperature measured before and after installation | F-1641 Mareș et al. Research on Best Solution for Improving Indoor Air Quality a… | machine |
Each row is one Finding — a sentence as printed in one study, recorded with its page in the Coridum Knowledge Base. Follow the Finding number for the exact wording and the citation. Checked says who verified the row: machine means every automatic check passed and the surrounding text was read; person means someone read the sentence in the document. Rows are re-checked by a person over time. The studies are curated in the Coridum Knowledge Base; the reading of them together is a Claim, shown separately.
Cite this page
Coridum Research. Radon mitigation. Coridum Knowledge G-0207, 16 September 2026. https://coridum.com/k/G-0207/