Air Duct Cleaning Air Duct Cleaning removes contaminants including dust mites, mold, mildew, bacteria, legionella and pollen.   Cleaning of Supply Vents & Return Vents Branch Vents Filters Furnace Fans & Motors When to have your air ducts cleaned... If an accumulation of contamination or debris is visually observed inside the duct. If the air smells bad. If the HVAC system discharges visible particles. For general health and hygiene - Every 3 years or as needed.