Mitigation
Post-mitigation verification
A new radon measurement carried out after a mitigation system is installed to confirm that it works. A long-term follow-up test is recommended, plus periodic re-testing over the years, since fans age and buildings change.
Related terms
Radon mitigationThe set of building techniques used to reduce indoor radon concentration, from sealing entry routes and improving ventilation to active soil depressurization. Well-designed systems routinely reduce levels by 50–90% or more.Sub-slab depressurization (SSD)The most effective and widely used mitigation technique: a suction point is created under the building’s slab and a fan extracts the radon-laden soil gas through a pipe, releasing it above the roof before it can enter the building.Sump depressurizationA variant of active soil depressurization that uses an existing sump or a purpose-built radon sump under the floor as the suction point. Common in buildings with drainage sumps or where a sump can be excavated from inside.Sub-membrane depressurizationThe equivalent of sub-slab depressurization for crawl spaces: the earth floor is covered with an airtight membrane and a fan extracts the soil gas from beneath it, preventing radon from mixing with the air under the building.Radon barrierA continuous airtight membrane installed in the floor or foundation to block soil gas from entering a building. Standard in new construction in radon priority areas; its effectiveness depends critically on sealing all joints and penetrations.