Roughly 30,000 skin cells are shed every hour per human which are circulated upto 60x’s per day in the vents. Whether at work or home, just imagine how many skin cells are generated by each person inhabiting the space every day. Choosing a duct cleaning company might now move a little higher on the list! No one wants to breathe in their co-worker’s dander.
Excess dust and debris can put undue stress on heating and cooling systems. If the furnace or air conditioner is working harder, it uses more energy, is decreasing the potential life of the heating and air units as well as increasing expenses unnecessarily.
Clothes not drying? Too Much Humidity? Could be a blocked dryer vent. Clothes dryers are responsible for approx 16,000 fires per year. Even if you clean your filter every time, particles can still build up in the hose which vents to the exterior of the house or dwelling. (and who knows if the people before you cleaned out the filter?).
Excess debris can build up on the heat exchanger be a fire hazard, and also encourages creepy crawly critters such as dust mites, pathogens, molds, and other health and allergen triggers.
A PDF from the US Environmental Protection Agency http://www.epa.gov/iaq/pubs/airduct.html .
Knowledge about Air Duct Cleaning is in its early stages, so a blanket recommendation cannot be offered as to whether you should have your air ducts in your home cleaned. The U.S. Environmental Protection Agency (EPA) urges you to read this document in it entirety as it provides important information on the subject.
The PDF file: Should-You-Have-the-Air-Ducts-in-Your-Home-Cleaned