Indoor air quality in a home or building can deteriorate for a variety of reasons. Since HVAC systems are installed to carry the air necessary for indoor comfort, they are usually one of the first areas checked when complaints occur.

Over the last several years, there has been a dramatic increase in the number of air duct cleaning firms. Some of these companies are not knowledgeable about HVAC equipment operation and duct design and construction. Others have failed to keep pace with improvements in duct cleaning methods and technology. Inadequate and ineffective cleaning of HVAC ductwork may actually cause and increase indoor-air-quality-related complaints among the occupants.

While several methods of duct cleaning are available, their effectiveness in reducing the level of airborne particulates in residential HVAC systems is unknown because there is a lack of established data and investigation. In an effort to fill the information gap, a study was initiated by the Building Construction Industry Advisory Committee (BCIAC) to evaluate which duct cleaning methods were effective and to what degree they were effective in improving indoor air quality. The results of the study published in May 1994 are outlined below.