NADCA, the National Air Duct Cleaners Association, recommends to have your air ducts cleaned every three to five years. An individual may want to consider more frequent cleanings under these listed circumstances:
Residents with allergies or asthma
Smokers in the household
Pet dander and hair
Water/ smoke contamination to the home
After home renovations or remodeling
Prior to the occupancy of a newly constructed home (construction debris)
Purchasing an existing home