The RadonAway RP145 is the most popular radon mitigation fan in the industry, is intended for use as a component of an active soil depressurization (ASD) system for reducing radon. The RP145 offer higher air flow, energy efficiency and quiet operation. It is ideal for both new construction and retrofit radon systems with a slab or membrane size of up to 2500 sq. ft. This fan is designed for moderate to good air flow, working most effectively with sub slab or sub-material conditions ranging from about 4 inches of clean, size 4-6 gravel to very loose soil. The RP145 is built to resist moisture and can be mounted inside or outside on a 3 in. or 4 in. schedule 40 PVC vent pipe using 3 in. x 4 in. or 4 in. x 4 in. flexible couplings. NOTE: When installing an ASD system for radon reduction, any openings, major cracks and penetrations in the building slab or membrane must be sealed. Fan sizing for retrofit may require professional diagnostics and design.