Does Air Duct cleaning prevent health problems?

The bottom line is: no one knows.  There are examples of ducts that have become badly contaminated with a variety of materials that may pose risks to your health.  The duct system can serve as a means to distribute these contaminants throughout a home. In these cases, duct cleaning may make sense.  However, a light amount of household dust in your air ducts is normal.  Duct cleaning is not considered to be a necessary part of yearly maintenance of your heating and cooling system, which consists of regular cleaning of drain pans and heating and cooling coils, regular filter changes and yearly inspections of heating equipment.  Research continues in an effort to evaluate the potential benefits of air duct cleaning.