There are two main types of duct cleaning equipment. The truck-mounted vacuum cleaning method uses a truck vacuum that is connected to the trunk lines of the ventilation system. This line draws a volume of air ranging from 10,000 to 15,000 cubic feet per minute. Rotating brushes are inserted into the ventilation grilles to help loosen debris inside and bring it to the collection point.
Some air duct cleaning technicians use a portable vacuum to clean the HVAC system, while others perform truck-mounted vacuum cleaning. The truck vacuum method (also called air sweeping) is meticulous and does an excellent job of carefully removing allergens and dirt. Whether or not you decide to clean the air ducts in your home, preventing water and dirt from entering the system is the most effective way to prevent contamination (see How to Avoid Duct Contamination). However, there is little evidence that simply cleaning the duct system will increase the efficiency of your system.
The disadvantage of air duct cleaning if you do it yourself is that it could ultimately damage the air ducts. Although it intuitively makes sense to clean the ducts, after all, you dust and clean the rest of your house, the fact is that the dust that settles on your ventilation system usually stays where it is, it is unlikely to disperse into the air unless you are disturbed. Before hiring a duct cleaning company, it is better to know the different methods of cleaning air ducts. When possible, access to the interior of the ducts should be through existing openings such as supply diffusers, return grilles, duct end caps and existing service openings.
If you or someone in your family has asthma or allergies, you may be considering cleaning the heating and air conditioning ducts in your home. Failure to clean all system components can re-contaminate the entire system, minimizing the benefits of cleaning. Most organizations concerned with duct cleaning, including EPA, NADCA, NAIMA and the National Association of Sheet Metal and Air Conditioning Contractors (SMACNA), do not currently recommend the routine use of sealants to encapsulate contaminants in any type of duct. You may consider cleaning the air ducts simply because it seems logical that the air ducts become dirty over time and be cleaned from time to time.
Whether or not you decide to clean your home's air ducts, it's essential to commit to a good preventive maintenance program to minimize duct contamination. This is because much of the dirt from the air ducts adheres to the surfaces of the ducts and does not necessarily enter the living space. If you suspect that there is a mold problem due to visible growth or a musty smell constantly coming from the supply grilles, the cleaning ducts won't do much good if they don't remove the mold. Cases where the use of sealants to encapsulate duct surfaces may be appropriate include repair of damaged fiberglass insulation or when combating fire damage within ducts.
However, many modern residential air duct systems are constructed of fiberglass panels or sheet metal ducts that are lined on the inside with a fiberglass duct liner.