Because they get dirty!
Accoirding to the National Air Duct Cleaning Association (NADCA) In addition to normal accumulations of dust and dirt found in all homes with air ducts, there are several other factors that can increase the need for regular HVAC system cleaning:
- occupants with allergies or asthma
- cigarette or cigar smoke
- fire, soot and smoke damage
- water contamination or damage to the home or HVAC system
- home renovation or remodeling projects
Some occupants are more sensitive to these contaminants than others. Allergy and asthma sufferers, as well as young children and the elderly tend to be more susceptible to the types of poor indoor air quality that air duct cleaning can help address.