As the years go on, your ducts accumulate a build-up of dust, pollen, dirt, mold, and other harmful pollutants. This build-up can be bad news for a number of reasons. First and foremost, that build-up is bad for your ducts, obviously, and should be cleaned out. Secondly, when you turn on your HVAC system, these pollutants are now circulating through the air in your house. If you’re already sensitive to the quality of air surrounding you (i.e. you have allergies or asthma), you can image what this type of air can do to you by re-circulating in your house all day. Thirdly, the build-up is bad for your entire HVAC system. Because the ducts are obstructed, your system needs to work much harder in order to push out cold air. This means you’re paying a higher energy bill and causing undue stress to your HVAC system.