How to Get Rid of Mildew in Vents

Open the main unit and check your filters. Dirty filters are a leading contributor to mold growth in vents, so first attack the problem at its source. Remove the filter and replace it if necessary. Otherwise, clean it according to the manufacturer's recommendations.

Check your system for moisture problems. Moisture should not collect in vents, and when it does, it points to a possible leak. Check for leaks in your cooling coils, which look like silver mesh screens in the main unit, and ensure that your condensate pan does not have excessive standing water. If you notice any problems in your unit, have it repaired before cleaning the vent mold, or the problem will just come right back.

Open all of the vents to check for mold. If you found mold growing in one vent, you may find it in others as well. Use a small screwdriver to open the screens and inspect the vents with a flashlight. If you find mold growing, put the covers back on the vents and turn on the main heating unit to dry out the mold.

Vacuum the inside of the dried vents to draw out the spores. Use a thin vacuum hose and set your vacuum to the highest setting possible. Do this after the vents dry completely, because it will not work if you still have moisture inside the vents.

Scrub the inside of the vents with a mild detergent and water solution, if you can physically see the mold spores. Just a drop or two of liquid detergent should do. When you thoroughly scrub the vents, scrub with a damp cloth to rinse the detergent and then turn on the heater once again to dry the vents. If mold returns, call an air conditioning and heating expert. The problem may originate in an area deeper than you can reach or observe.