Every time our central HVAC unit kicks on lately, I have been noticing an odd musty odor that starts to come out of the air vents… It’s not exactly a disgusting odor like sewage or a rotting pet or anything horrific like that, so I’m not afraid of a leak or something dead in our ventilation system… But still, you don’t want to dread having your HVAC unit kick on because you think that the whole home is going to odor odd again in a matter of hours, either. I did a little test just to see if maybe there was something wrong with our air filters. I wondered if that I had just waited too long to change them plus they were starting to odor in a funny way or something, however so I bought some current HEPA filters plus updated all the seasoned air filters with them! At first, the odor seemed to be a little better. But then I realized that this was because of the quality of the HEPA filter itself, not due to the source of the odor was gone. I finally provided up plus called our local Heating plus Air Conditioning company to get them come out plus do an HVAC duct cleaning for me, then they showed up for the appointed time with their special HVAC duct cleaning unit plus got to work. They found a couple of tiny cracks plus leaks as they were removing the debris plus dust. The Heating plus Air Conditioning specialist told me that if you have cracks plus leaks, sometimes black mold or mildew may build up inside the HVAC duct plus cause odd odors. They finished the HVAC duct cleaning plus ever since then, I haven’t noticed any odd odors at all. As a matter of fact, I think that our indoor air pollen levels are much better now.