Your heating and cooling system is the lungs of your home. The system takes air in and breathes air out. Through normal occupation in a home, we generate a great deal of contaminants and air pollutants, such as dander, dust, and chemicals. These contaminants are pulled into the HVAC duct system and re-circulated 5 to 7 times per day, on average. Over time, this re-circulation causes a build-up of contaminants in the duct work.