Loosen the straps or unzip end connections holding the HVAC duct in place. Separate long sections of fabric ducting for easier transport and cleaning. Turn the material inside out to expose the dust covered surfaces.
Load sections of textile duct into a large capacity washing machine until it is half full. Add the manufacturer's recommended amount of laundry detergent. Run the washing machine on a standard cold wash cycle.
Move the cleaned HVAC duct sock to the dryer. Set the dryer for a low heat cycle. Remove the duct sock from the dryer while it still is slightly damp.
Lay the ducting material out flat on a clean surface. Reconnect the duct sock sections once they have completely dried.