Air Duct Cleaning is also known as the "push and pull" method. First we drawing a very high-powered vacuum from the plenum at the furnace (supply and return duct), while simultaneously "air washing" the duct system with our patented 250 p.s.i "skipper" (high pressure nozzle) propels itself down the Air Duct run until reaches the plenum or major trunk line. This is why you should always call for professionals to do your Air Duct Cleaning.