Mitigation
Sub-membrane depressurization
The 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.
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.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.Radon fanThe in-line fan that powers an active soil depressurization system, running continuously to keep the ground under the building at lower pressure than the interior. Fans typically last 5–15 years and should be checked periodically, often with a pressure indicator.