Indoor Air Quality: Duct Cleaning Air duct cleaning is the physical cleaning of heating, ventilating, and air-conditioning (HVAC) system components including ducts, air terminals (supply and return), heat exchangers (heating and cooling coils), condensate drains and pans, fan motors and housings, system filters, and the air handling unit housing. However, little published data exist on the impact of air duct cleaning on residential indoor air quality or energy costs (Kulp, et al.).