A radon mitigation system is any process or system used to reduce radon concentrations in the indoor air of a building. The goal of the system is to reduce the indoor radon level as low as reasonably achievable, ideally below the EPA action level of 4 pCi/L (picocuries of radon per liter of air) . The most common method of radon mitigation is sub-slab depressurization, which involves the installation of a fan and venting system to draw radon gas from the soil and expel it outside. Other methods include drain tile depressurization, sump hole depressurization, and block wall depressurization. The right system depends on the design of the home and other factors. The effectiveness of a radon mitigation system depends on several factors, including the buildings design, soil type, and radon levels. Sealing cracks and other openings in walls and floors in contact with the ground is also important, as it limits the flow of radon into the home and makes other radon reduction techniques more effective and cost-efficient.