With increasing attention focused on health concerns from biological contaminants and dust in the indoor environment, the American Lung Association recommends the use of duct cleaning:

Duct cleaning has not been shown to prevent health problems, nor is scientific evidence currently available to conclusively demonstrate that particle (e.g. dust) levels in homes increase because of dirty air ducts. The U.S. Environmental Protection Agency does not recommend that air ducts be cleaned routinely, but only as needed.

When health problems are believed to be the result of biological contaminants or dust in indoor air, it is important to first determine that contaminated ducts are the cause of the health problems and verify that the ducts are, in fact, contaminated. The source of the problem may lie elsewhere, so cleaning ducts may not permanently solve the problem.

People who have their ducts cleaned should verify that the service provider takes steps to protect individuals from exposure to dislodged pollutants and chemicals used during the cleaning process. This may involve using HEPA filtration when cleaning, providing respirators for workers and having occupants vacate during cleaning.