Learn about air duct cleaning in Raleigh NC and find out what is what is air duct cleaning and what air duct cleaning cost. Removing all air born dust and debris from the ducting systems of Forced Air Systems, Gravity Heaters and HVAC Systems. The duct system is put under negative pressure either from the motor area of the unit or from the return air. During the negative pressure stage, compressed air is shot into the air duct system through the register/vents termination of each duct. The entire system is gone through in this manner and then the motor area is cleaned out.