The process begins with an inspection of the entire air duct system prior to cleaning. This includes testing the heating and cooling system to make sure it is operating properly and there are no possible leaks in the duct system. Next, the technician will wrap the furnace filter in plastic to separate the supply and return sides of the system and then mask off the return grills. After creating an access hole in the ductwork on on the return side, a vacuum hose is connected to the ductwork. The vacuum source is checked for proper negative pressure and starting from the furthest grill, the grill and the ductwork are cleaned with air tools and brushes. Once the return side has been cleaned, the process is repeated on the supply side.