There are many reasons to clean the ductwork in your home. When ductwork are clean, the heating system lasts longer (because there is less dirt wearing out its components), we dust less often, and the air we breathe at home is cleaner. For those of us with allergies, this should be a welcome improvement.
Probably you don’t own a high-powered, truck-mounted vacuum system with 150 foot-hoses; perhaps you can’t afford the cost of such service.
There are many different designs of ductwork systems, such as attic systems and underground systems, but the theory of clean ductwork systems is the same. You may not be able to access all parts of these systems (for example, underground ducts), but you can make a difference in your air quality by cleaning the parts of the system that you can reach.