Compressed-air is your best option to choose when it comes to cleaning round as well as rectangular shafts and air ducts. The compressed-air cleaning equipment is available in different sets. Round and oval ducts can be effectively cleaned by the backward rotating helicopter nozzles. The air whips are being used in square and round air ducts, where they loosen even firmly bond dust. The used compressor should be capable of a permanent output capacity of at least 70 psi at a minimum volume flow of 14.7 CFM.