The HP 2133 is best used when you have good slab communiciation and you don't need much air flow. Max. air flow 134 cfm and an enery efficient fan - only 20W! Fantech's HP series fans are specifically designed for radon mitigation systems. The fans are sealed tight to reduce re-entrainment risks and the motors are built to run 24 hours a day every day. This fan is approved for indoor use which is important in Canada's cold climate. 5 year manufacturer warranty. Made in Germany.