Signs of Mold in HVAC Ducts and How It Affects Indoor Air Quality Most people do not think much about what is happening inside their air ducts. You turn on the AC or heat, and air flows. That is it. But sometimes, what is flowing through those ducts is not as clean as you expect. One common but overlooked issue is mold in HVAC ducts. Read More : https://www.serviceplus.com/blog/signs-of-mold-in-hvac-ducts-and-how-it-affects-indoor-air-quality