What Kind of Mold Grows in Window ACs (& How To Prevent It)

No one likes having mold in the house; these tiny spores can spread quickly and negatively affect people, especially those with chronic lung or health conditions. One of the worst but most common places for mold to grow is your AC unit.

If you find mold in your window ac unit, read on to discover how to remove and prevent it from occurring in the future.

What Kind of Mold Grows In Window Air Conditioners?

Mold is more of an umbrella term referring to the wide variety of strains and types, many of which can be bad for your health. What kind of mold grows in air conditioners? Some of the more common types include Stachybotrys, or black mold, along with some others discussed below.

What Mold Grows in a Window AC

Stachybotrys (black mold)

Also known as black mold, Stachybotrys is a common type of mold that forms a spreading back substance. It’s one of the more easy-to-spot types of mold that can grow in your AC unit, but they are also some of the more toxic molds to find there.


Fusarium is often found in areas affected by water damage. However, it can be found in other moist areas such as humidifiers and stagnant water. It is prevalent in the summer or humid and warm conditions. It looks white and fluffy and can have red lines or splotches in the middle.


Another white and fluffy-looking type of mold, Acremonium, needs damp environments to grow. It can often be found in hay or other dead plants as well as AC units. One area you are most likely to find this type of mold in your AC unit is in the humidifier water.


One of the more aggressive types of mold, Trichoderma grows over time in areas like air vents. Trichoderma typically looks like spores and rapidly multiplies if not taken care of. You can also find this mold in parts of your window air conditioning unit that are constantly moist or damp.


Alternaria is another common mold often found in running water areas, flooded areas, and humidifiers. It appears green or brown in color and has a velvet or powdery appearance. In terms of your air conditioning unit, you can find Alternaria in the air ducts or vents and other parts of the AC unit.


Mucor is a hazardous mold that must be taken of as soon as possible. Commonly found in the vents or various parts of your air conditioning unit, the spores often creep into the unit via the windowsill itself. It does this by spreading until the spores enter the air conditioning unit.

Why Are AC Units Prone To Mold?

Mold spores are everywhere. They are a natural part of our world that can easily find a way into our homes. To survive, mold needs damp and dark spaces with plenty of moisture and organic food sources.

AC units regularly deal in condensation and humidity, making them decent breeding grounds for mold, especially when combined with organic particles like dust, pollen, and skin particles.

When it is hot and the water in your AC unit heats up, your AC becomes the perfect home for mold in window air conditioners of various types. The coils, vents, filters, and ducts and vents are most susceptible to molds in these conditions.

Common Signs Of Mold Growing In Your AC

  1. .A musty smell
    If you notice a musty smell near your window AC unit, that could be a sign of mold living and growing inside it.
  2. .Increasing distinct odor increases when running
    Suppose turning on and running your AC unit only increases this distinct musty odor, and that does not disperse after a few minutes. In that case, you are likely to have mold inside your AC unit.
  3. .Visible patches around the vents, evaporator coils, or drip pans.
    If you can see black, green, white, or other mold growths around the vents, parts, or casing, that is a sure sign that the mold has most likely grown out of your AC unit.
  4. .Allergies won’t go away
    If your allergies only seem to get worse in your home despite having the windows closed and the air conditioner on, that is another sign that mold may be spreading throughout your house via the AC unit, exacerbating your symptoms.

The Health Risks & Dangers of Mold in the Home

But what are the mold in window air conditioner health risks? Just some of the outcomes of inhaling mold include:

  • Nasal stuffiness
  • Throat irritation
  • Coughing
  • Wheezing
  • Eye/skin irritation
  • Serious infections for immunocompromised or chronic lung illness sufferers
  • Aggravated asthma symptoms

Mold in your AC unit is not necessarily more dangerous than other mold found in your home. However, those types of mold can spread quickly and efficiently from your AC unit to other areas of your home while in use. This can cause issues for your health and cause mold to grow elsewhere in your home.

How to Demold & Clean A Window Air Conditioner Unit

How can you clean a window air conditioner with mold? Yes, you absolutely can. Being prepared, regular, and thorough is the key to removing mildew from your air conditioner unit. Can you clean mold inside a window air conditioner? Yes, provided you disassemble it beforehand. Here’s how to start cleaning:

  • Toolbox
  • Safety mash, gloves, and goggles
  • Protective clothing
  • Flashlight
  • Bleach
  • Tilex
  • Dish soap
  • Hot water
  • Cloths and sponges
  • Nylon brush
  1. .Put on your safety gear and ensure that the room is adequately ventilated.
  2. .Shine a flashlight into your unit and look for mold. If more than one-third of the unit is covered in mold, we recommend replacing the unit entirely.
  3. .If less than 1/3 of the unit has mold, disassemble the unit according to the manual instructions. We recommend unplugging the unit before disassembling. You may need another person with you to put the unit on the ground once it is removed.
  4. .If you have black mold, we recommend spraying the parts, especially the filter, in Tilex and leaving it for 15 minutes. Scrubbing the parts thoroughly before leaving them can help. Once done, rinse the parts before vacuuming the cover and grille, wiping everything with a wet cloth, and leaving it to dry before reassembling.
  5. .If you do not have access to Tilex, try mixing half a cup of bleach, one tablespoon of dish soap, and three gallons of hot water. Scrubbing the parts with this mixture can be an effective way of removing mold. Once the pieces are cleaned, rinse them and leave them to dry before reassembling.
Demold and Clean a Window AC

How to Prevent Mold In A Window AC: Long Term Tips

Once your air conditioning unit is clean, the key is to prevent the mold from building up again. But how to prevent mold from growing in window air conditioners? The key is to control moisture and dust levels. Some ways to prevent mold in air conditioners include:

  • Ensuring that your window unit sits tightly in your windowsill
  • Ensuring that your window unit is slightly tilted towards the window for proper drainage
  • Clean the filters and grates regularly to prevent dust buildup
  • Dust your unit every few weeks
  • Cover your unit with a towel when not in use
  • Inspect your unit regularly for mold or dust
  • Don’t turn your unit off if going away during the summer or hot weather – this is when mold and dust can get a foothold
  • Use fan mode to dry the interior of the air conditioner, if applicable
  • Invest in both an air purifier for mold and a dehumidifier for mold as these can help also.

People Also Ask (FAQ)

Does bleach kill mold?

Bleach can kill mold depending on the surface the mold is on. Bleach will not work on a mold that has grown on porous surfaces such as wood or drywall.

Does vinegar kill mold in air conditioners?

Vinegar can clean the mold from your air conditioning unit but be wary that it can damage your unit’s parts. We recommend diluting it with water to prevent that from happening.

How long does it take for mold to affect you?

That depends on your health and the concentration of mold in your home. Various factors affect the speed of infection and how that will impact your health.

Will mold die if it dries out?

When mold dries out, it does not die. Instead, it simply becomes temporarily inactive. Once moisture is reintroduced, it returns to being a persistent threat if not removed from your home.


Your air conditioning unit is an excellent tool for taking care of your loved ones. Taking proper time to inspect and care for your unit prevents mold from causing problems in the future. Following our recommendations above, while adopting regular cleaning and inspection habits, should prevent mold from building up and causing problems in your home.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.