How to Kill Mildew in Air Conditioning Vents

Kaye Wagner

Mildew is a type of fungus that grows in damp and humid areas. If you live in a wet climate, such as a Southern state or tropical country, it is likely that you’ve had to clean mildew off your bathroom walls, basement floorboards or even from behind your wallpaper.

Air conditioning vents can transport mildew to any room in your home.

Mildew can also often grow inside air conditioning vents. This is especially a problem for those with asthma who may be sensitive to mildew spores. You can kill the mildew with a homemade solution. Use long-handled products to make it easier to reach deep into your vents.

  1. Turn off the air conditioning vents so that the mildew spores do not continue to spread and so the cleaning solution does not spray back in your face.

  2. Mix 1 qt. of warm water with 2 tbsp. of chlorine bleach.

  3. Pour the mixture into a spray bottle and spray as far as you can into your air vents until the mildew growth is completely soaked. Also soak the sides and ceiling of the air vent to ensure that any microscopic mildew growth is also covered. Use a ladder to get better access into the vent. Let the solution sit on the growth for at least 20 minutes.

  4. Scrub the walls, ceiling and floor of the air vents with a long-handled brush. Scrub the back of the vent before scrubbing the area closest to you.

  5. Fill another spray bottle with clear water and spray the entire air conditioning vent to rinse away the chlorine.

  6. Wipe down the walls completely with paper towels. Use a sponge mop to dry the areas if you are unable to reach them. Dry the areas completely to ensure that any leftover mildew spores are not attracted to the damp area.

  7. Tip

    If the mildew returns, consider consulting a professional, who is able to kill the mildew spores with a high-intensity vapor. Install a dehumidifier to remove the moisture in your home’s air. This will help prevent mildew from growing. Always clean in a well-ventilated room.


    Wear goggles, a face mask, pants and a long-sleeve shirt.