Mold in Window Air Conditioner and How to Get Rid of It

Black mold in a window air conditioner is nasty stuff! It should be removed before it causes health issues to those with susceptibility to breathing and lung problems.

Mold on Window AC Styrofoam and Other Locations

Window Air Conditioner Black Mold

Sometimes you know there is black mold in a window air conditioners because of the musty, tell-tale smell when you turn it on or it’s been running for a while.

People allergic to mold sometimes know its nearby when allergy symptoms start – sneezing, coughing, an asthma attack, watery eyes, etc.

Other times window AC mold is visible on the filter, housing or when you peer into the interior of the unit.

Whatever the clues, mold should go – and there are steps you can take to keep it away too.

What Causes Window Air Conditioner Black Mold?

Knowledge is power! Knowing what causes window AC mold will help you to prevent it again once you’ve cleaned your AC.

Three things are needed for black mold on a window air conditioner. At the end, we talk about how to deal with the moisture and nutrients part of the equation.

  • Mold spores – Mold is common. Mold spores are found in most homes. By themselves, they might not pose a serious threat.
  • Moisture – When spores get wet, they begin to grow and reproduce. This is why the US Environmental Protection Agency (EPA) says, “the way to control mold growth is to control moisture.” However, since your window AC dehumidifies the air in the room – gets rid of moisture – this is difficult, and it is why black mold on window air conditioners is so common.
  • Nutrients – Mold needs food. That’s why it does so well on old forgotten food in the refrigerator. And this also offers a hint to keeping mold off your window air conditioner. Starve mold by keeping the AC clean.

The EPA’s guide 10 Things You Should Know About Mold is good reading for anyone concerned about mold in air conditioner health risks and how to prevent them. The guide includes many useful links too.

Mold in Air Conditioner Heath Risks

Most people won’t be bothered by small amounts of black mold on the air conditioner.

However, mold in air conditioner health risks are real for people and pets that have asthma, COPD, allergies and other breathing problems. Black mold is danger for older people and their beloved pets regardless of general health when mold spores are breathed.

Black mold’s technical name is Stachybotrys chartarum. According to the Centers for Disease Control & Prevention, “Stachybotrys chartarum and other molds may cause health symptoms that are nonspecific. It is NOT necessary to determine what type of mold you may have growing in your home or other building. All molds should be removed.

How to Remove Mold from Air Conditioner Ducts and other Parts

You’re here for this information, and we provide step by step mold removal instructions.

Here’s your supply list to remove AC mold:

  • Safety first – Face mask and nitrile or latex gloves. You might want to slip leather/mechanics gloves over the nitrile gloves when cleaning the fins or interior of the AC. There are sharp parts to avoid.
  • Window AC Cleaners – Antibacterial dish soap for the washable filter, Tilex or similar cleanser that lists on its label that it kills mold. If you don’t have antibacterial dish soap, the Tilex can be used on the filter. We prefer Tilex because it is specially formulated to kill and remove mold and mildew.
  • Cleaning Tools & supplies – Nylon scrub brush, cloth rag or paper towel, vacuum cleaner with crevice tool and upholstery brush.
  • Hand tools – Screwdriver set.

How to Clean the Washable Filter:

clean washable window ac filter

This is an easy first step to get you rolling.

If there is black mold on the frame of the filter, spray it with Tilex, let it sit a few minutes, and wipe it off.

Then proceed with general AC filter cleaning:

1). If you have antibacterial dish soap, put the stopper in a utility tub, bathtub or large sink. Fill it with 2” of water, and pour in a liberal dose of dish soap. Swirl it to mix the soap.

2). Remove the grille from the front of the AC and remove the filter, or simply slide the filter out of its slot (if that’s the AC design). Most grilles have clips; a few have screws.

3). Drop the filter in the soapy water or spray it on both sides with Tilex. Let it sit for 15 minutes (longer won’t hurt).

4). Gently scrub both sides of the filter with the nylon brush. Rinse the filter well, shake it gently to speed up the drying. Hang it up or gently towel it off, and allow it to dry. Done!

How to Clean Mold from a Window Air Conditioner:

OK, with that success behind you, turn your attention to the rest of the unit.

1). Pick your Spot: Move the unit to a well-ventilated space where you can easily get to both sides of it. A workbench in the garage or a picnic table outside are two common options

Note: This is a good time to put on the gloves and mask for protection against mold, cleaners and sharp parts

2). Get Into the AC Interior: The grille should be off. Remove the screws holding the metal cover at the front of the AC – it was immediately behind the grille.

3). Suck it Up: Use the vacuum hose to remove loose dirt, dust, yard clippings, etc. from inside the AC. The crevice tool might come in handy.

4). Brush the Fins: Attach the upholstery brush to the vacuum, and gently clean the fins on the AC coil. Work the brush in the same direction the fins run. Be gentle to make sure the fins don’t bend.

5). Clean the Fins: Once the debris is gone from the radiator-like fins, spray on Tilex. Allow it to sit for 15 minutes, brush it lightly and rinse it off with a hose or water from a spray bottle.

6). Clean the Housing: Spray off the housing – the part that sticks out the window. Let the cleaner sit, and then wipe or rinse it off.

7). See Any Mold Inside? This is how to remove mold from air conditioner ducts – the passageways that cycle air from inside through the unit and back into your room – and those on the outside that carry away heat.

If there is mold on Styrofoam insulation or mold in the ducts, spray Tilex on the moldy spots. Let the cleaner sit for 15 minutes, and wipe it off with paper towel or the cloth. If using paper towel, throw it away, and grab a few new sheets when needed.

8). General Interior Cleaning: Now that the nasty spots have been cleaned, spray down the rest of the interior. This won’t hurt the AC, since it is built to be moisture-resistant. Allow the cleaner to sit for 15 minutes. Wipe it out with a cloth or paper towel.

9). Don’t Forget the Cover and Grill: Spray down the pieces you removed. Allow the cleaner to sit, and wipe off or hose off the cover and grill.

10). Dry, Assemble & Go: Give everything time to dry. Sure, ACs are supposed to be water resistant with waterproof wiring and attachments, but it is better to be safe.

Reattach the cover and grille.

If possible, plug in the AC and run it on the workbench or outside for a few minutes to get the cleaner’s chemical smell out of it. You don’t need that in your house! It can trigger allergic reactions just like mold can.

Once it airs out, it’s ready to return to the window opening for use. Here’s a 10-minute video that covers many of the same tips and a few different ones.

How to Prevent Mold in Window Air Conditioners

Now that the black mold in the air conditioner is gone, keep it away with these tips to deprive it of food and water!

1). Remove Dust: Mold feeds on dust and dirt. If you dust or vacuum away dust, dirt, pollen and other organic materials, you can “starve” any mold that begins growing. Using compressed air to blow dust out the back of the AC might help too. Some people cover the inside part of the AC with a towel when not in use to prevent it from getting dusty.

2). Use Fan Mode to Dry the Interior of the AC: Most window air conditioners have a Fan setting. The compressor won’t come on to remove heat, but the fan will blow. After you’ve cooled the room, turn on Fan Mode.

This will dry out the interior of the air conditioner – and as the EPA reminds us, moisture control is the key to mold control.

3). Clean your Window AC Once or Twice During the Cooling Season: If you live in a hot climate, especially one that is humid too, clean your AC at least twice during the cooling season. Inspect it monthly for mold.

If your AC doesn’t get heavy use, then cleaning it once during the season should be sufficient unless you or someone in your household is especially sensitive to mold.

Is Mold a Problem in your Home?

If mold seems to plague your home, there’s a problem somewhere.

Your Central AC System – If you have central air conditioning, mold can build up in your ducts. This is especially true if your ducts are the wrong size and/or if your AC or heat pump is the wrong size. These issues might not allow the dehumidification process that goes with air conditioning to be complete enough. Water condenses on cold, dusty ductwork sheet metal, and mold spores have all they need to grow.

We highly recommend having the system looked at by an HVAC professional. Getting two opinions about what the problem is and how to solve it is a good idea.

Your Home or Building – You should definitely try to eradicate mold in your home or building. If that’s not possible right now, or until it is done, an air purifier designed to remove mold spores from the air is a good short-term solution. Once the mold has been removed, the air purifier will keep your air cleaner and more breathable.

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