A system for cleaning building ductwork utilizing the equipment generally used to clean carpets. The system utilizes the vacuum unit and liquid waste tank from a carpet cleaning system. A flexible hose runs between the waste tank and the building ductwork. A water injection system is connected to the hose and is used to spray a stream of water into the air flowing through the flexible ductwork which will entrap any particles contained therein. The "dirty" water flowing out of the hose will flow to the waste tank for collection and disposal.