Modern houses and apartments are built to be airtight for greater heating and cooling efficiency. They're so airtight, however, that new air circulates back into the house very slowly - it may take hours for the air in a new house to recycle itself.
This creates not only stale air but a buildup of indoor pollutants. These pollutants include irritants such as dust, smoke, mold spores, pollen, and animal dander which not only bother your lungs but clog heating and cooling systems, computers, and other electronic equipment. You may also suffer the effects of more serious environmental hazards such as the outgassing of formaldehyde from construction materials.
The simple steps below will help you clean your ducts, though a professional cleaning can access ductwork which a homeowner can't reach.