With regular use, a furnace’s white filter will slowly turn dark. If the color darkens to black, this should raise a few concerns. An underlying problem might exist, although the issue could be easy to address. In some cases, however, the sight of a black filter represents an alarming problem. Don’t ignore the issue. Let it nudge you to act right away.


A filter acts somewhat like a net as it captures dirt, dust and more. If you don’t change the filter at the right time, the buildup becomes significant. As time wears on, the filter may go from black to gray. Now, the filter might not be able to do its job properly, and the furnace could overheat, leading to damaged parts or worse.

Requesting routine maintenance from a reputable heating and cooling company could potentially prevent this problem and others. Quality Star Services of San Antonio can assist with maintenance, repair and installation work. Our excellent BBB rating should instill confidence in would-be customers.


Moisture could collect inside a furnace, which means mold may grow on the filter. Black mold could create a serious health risk. The possibility exists that toxic mold spores may travel through the ducts and blow out with the air. So, you don’t want to delay in killing off any mold in the system. A thorough cleaning of the system might not be enough, and a mold removal team may need to be called.


Carbon monoxide is a poisonous gas produced by the furnace’s combustion process. If there is a leak in the line, the odorless, colorless gas will come out, and it can turn a screen black. A leaking carbon monoxide line presents a dire health hazard. Hopefully, the home has a carbon monoxide detector to pick up on its presence.

Quality Star Services in San Antonio, TX, has served thousands of customers since opening for business years ago. Our NATE-certified technicians are available to help with requested heating/cooling work along with air quality and ductwork jobs. Call us today to see how we can help you.