Cleaning of residential ductwork is important for your health as well as your safety. The average house can have up to 3/8” of dust lining the return air duct that with a single spark could flash fire throughout the system. I have mentioned specifically the return air as the air entering these opening is not moving as fast (lower velocity) and is not filtered like the supply air outlets. The lower velocity of the air allows gravity to take over and the airborne dust can settle on the bottom side of the joist space.
Return air inlets in residences are not always metal on 4 sides. Wall cavities used for return air are drywall on two sides and wood studs on the other 2. Return air chases under the floor are wood joists on 2 sides, wood flooring on top and either drywall boarding on the underside or a thin sheet of metal if in the basement. In an ideal world there would be return air in every room of a home (except bathrooms and kitchens). The combination of these materials grabs dust and holds it before it can reach the air filter. The buildup in the return air is more than just dust. Pet hair, dander, insects, mold and bacteria make up the debris in the returns. The homeowner can push the nozzle of their central vacuum down the opening when the grills are removed, but it is very easy to get your vacuum hose snagged and unable to be retrieved. Your home vacuum will not provide the same level of cleaning as the power brushes and vacuum of the professionals. Remember that it does not matter how good your filter system is if the dirt does not reach the filter. I have seen the “before and after” and was amazed at the amount of junk they can remove from a system. It is a noisy process with air lines and scrubber brushes banging about in your ducts and not something you wish to schedule at the babies’ nap time. You can get a very close approximation of the cost over the phone by counting the number of supply and return registers in the home. I have provided my customers with the names of two Companies that have performed without complaint or negative feedback to me for cleaning ductwork. They are, Ontario Duct Cleaning at 1-800-ONT-DUCT and Ontario Power Air Duct Cleaning at 905-670-8870.
They will open a few access points in the duct system and cover them and also drill several holes that will be plugged when complete. When the job is complete it is important to check the air flow at each of the supply outlets as their high pressure air hoses may have changed the position of some of the balancing dampers.