The most common and most effective methods of reducing radon levels in a home or building are active sub-slab depressurization (ASD), and active drain tile depressurization (ADD) systems.
Active Sub-Slab depressurization:
Active sub-slab depressurization is a technique used to collect soil, including radon, from beneath the concrete floor slab in the lowest levels of the home. This is done by drilling a suction point (a hole that is typically 4-inches in diameter) through the floor slab, and installing a 4-inch diameter PVC pipe into the suction point. This piping is then run from the suction point to the exterior of the home.
A vent fan is placed in line with the piping on the exterior of the home (or in the attic) to create negative air pressure under the floor slab. The radon and other soil gases are then drawn from beneath the slab and into the system piping where they can be vented safely outside. In many cases, this piping can be run through the home (garage, closet, attic, etc.) and roof to help conceal the system.
Active Drain Tile Depressurization
When a home has a drain tile waterproofing system around the foundation, the drain tile can facilitate collection of the soil gases, while at the same time functioning as a waterproofing system. The sump pit is covered to create an air tight seal, with the sump pump (if present) being routed through the cover.
A hole (suction point) is drilled through the sump pit cover or the concrete slab to access the drain tile/sump pit, and four-inch diameter (typically) PVC pipe is placed into the hole, and travels from the suction point to the exterior of the home.