An indoor air duct can be cleaned by removing the vent from the wall and vacuuming dust from the vent and the air duct with a vacuum hose or brush. The vents and opening to the air duct can be wiped down with warm water, dish detergent and vinegar.
When preparing to clean indoor air ducts, fill a bucket with dish detergent and warm water to wash the vents and interior area of the ducts. If mildew or mold is present in the ducts or on the vent, wear a protective face mask and apply a mold removal spray on the areas. For tough stains or buildup, spray vinegar from a spray bottle to loosen debris and dust before thoroughly scrubbing the vents and air ducts with a mixture of dish detergent and warm water. Although cleaning cloths or rags may remove most dust and dirt, it may be necessary to scrub some areas with a sponge or scrubbing pad.
Before cleaning, the vents should be unscrewed and removed from the air duct to thoroughly clean both sides of the vent and access the air duct. It may be necessary to use a ladder to access air ducts on the ceiling.