During the Advanced Air Duct Cleaning, the beginning of the process is the same as for the Standard Air Duct Cleaning. The technician attaches an industrial vacuum hose (about 6 inches in diameter) to the ductwork near your furnace, creating negative air pressure throughout the ventilation and duct system. To do this, he creates an access point (a hole), using a drill and tin snips, that will later be covered with a piece of galvanized sheet metal (otherwise know as a cover plate). If you already have an appropriately positioned access point, he will use the existing one.
Once the access has been created and the vacuum is in place, the technician then services each supply and return vent with an air wand. This device has a nozzle approximately one foot long. It is pliable and fits in between the fins of the registers, exerting roughly 200 lbs. of air pressure. The technician is able to angle the air wand to force any dust and debris down the branch lines and into the main trunk lines.
After the technician has serviced each of the vents with an air wand as described above, the Viper Clean Sweep is employed in the main supply and main return ducts. The Viper utilizes six 14-inch long tentacles that thrash vigorously in every direction inside the ducts, loosening debris from every nook and cranny and sending it down the main trunk and into the vacuum. The Viper is particularly effective in removing debris from the corners of the ductwork (where a rotary brush can sometimes miss), and is one of the most thorough duct cleaning tools available.
It is generally recommended that the furnace filter be replaced after air duct cleaning, but if a new filter is not immediately available, the technician can clean your existing one with air pressure (outside your home, of course!) until a new one can be obtained, typically within a week. This will also give the furnace time to cycle through any residual dust that may remain in the system.