If you can answer yes to any of the following questions, then it may be time for you to call Dick's Vacuum Service:
The most effective way to clean air ducts is by using a truck mounted vacuum. Your system is placed under negative pressure. While the vacuum draws air through the system, various tools are inserted into the return and supply register to dislodge contaminants and debris. The powerful vacuum pulls the contaminants out of the air ducts, removing them from the system and your home with no mess left behind. The final steps are to clean the plenum, furnace, heat exchanger, evaporator coil, condensate drain pan and the blower housing, motor and wheel.