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Can Air Conditioners Get Moldy?

Molds and mold spores can cause various health effects, especially to those with mold allergies or any underlying lung disease. Molds can easily enter your household through any and every opening.

Your air conditioner can get moldy if left unused for a while. This is more likely to happen during the colder months of the year. Molds can travel in the air in the form of spores, which cause them to stick and grow on a huge variety of surfaces, which happen to include your air conditioner.

The rest of this article will explain the dangers of mold growth left unchecked, how mold gets into and grows in your cooling unit, how to inspect the cooling unit for mold growth, how to get rid of molds, and precautions to take to prevent it.

Can Air Conditioners Get Moldy?

The health implications of mold growth left unchecked.

The danger of leaving mold growth in your cooling unit lies in how your cooling unit works. It works using the vapor-compression cycle between gas and liquid states to remove heat from the air and circulate the cooled air. 

Spores would be efficiently distributed across your household with this cooled air through the HVAC ductwork. Over time, this circulation of mold congested air will spread to other parts of your home.

Mold can be spread easily through the air inhaled, but what does it do to the body? According to the CDC, the effects of the mold on the body vary depending on your sensitivity to molds. 

It could trigger symptoms like wheezing, coughing, irritation to the skin, sore throat, sneezing, stuffy nose, headaches, watery or itchy eyes, etc. People with respiratory issues can have even more severe and intense reactions, as do individuals with a compromised immune system.

How mold gets into and grows in your air conditioner.

The most common mistake made by homeowners that leads to molds entering their air conditioners is failing to change their filters. Filters are put into your air conditioner to prevent pollutants like dust, pollen, and microspores from entering your household. Mold will only grow if the conditions are right.

The presence of moisture in your air conditioner can come from a leak in the evaporator and condenser coils, which has the potential for this as it is constantly circulating the refrigerant. The debris and dust that settle in the unit serve as the mold’s food source. Moreover, the alternating low and high humidity in your air conditioner will promote mold growth.

Can Air Conditioners Get Moldy?

Inspecting an air conditioner for mold.

The symptoms mentioned above are common to several respiratory infections, so it is important to confirm that your air conditioning unit has mold before you determine if the problem is small enough for you to handle or large enough to call for professional help.

  • Check for a musty smell in the room in which the vents are located.
  • Check for any visible mold in the vents

You may need to remove the front grille cover (a screwdriver may be needed depending on the installation) and inspect the grille using a flashlight. Molds appear as streaks or clusters of brown, black, white, or greenish stains. Mildew, a common form of mold, appears as a powdery gray or white stain or streak.

If you find these traces of mold, you should proceed to clean the air conditioning unit, but before you begin the cleaning process, you should seal up the infested vents with nylon to contain the spread of mold spores for the time being. 


How to get rid of mold.

The importance of safety can not be stressed enough as you will come in contact with chemicals during the cleaning process. Make sure to use a face mask, a pair of goggles, gloves, and any extra safety equipment you find convenient. 

Remove the cooling unit from the wall or window

You will need a screwdriver to remove the air conditioning unit from its frame, and you might need help when removing it from the wall, depending on how heavy the air conditioner is, so be sure to have someone close by to help with this heavy lifting.

Disassemble the air conditioning unit

Remove the grille and filter on the front of the unit. If the mold is visible on the filter, it should be soaked in a sink filled with diluted bleach (about 1/4 cup of bleach) in water. After this is done, you remove the top and back of the unit and clean the inside of the air conditioner. Since the unit will have some hard-to-reach places, a handy vacuum cleaner should be used.

Can Air Conditioners Get Moldy?

Clean the coils

Next up, the evaporator and condenser coils have to be cleaned of the gunk on them. This is an alternative breeding ground for mold in the air conditioning unit. A home detergent can be used for little streaks of mold, but bigger molds could require a commercial coil cleaner. 

The coil cleaner may come in a spray bottle or not, depending on what you buy. If it doesn’t come in a spray bottle, rinse out any spray bottle you have thoroughly and pour some of the coil cleaner liquid into it. Another option is to buy some spray bottles along with your order or in a supermarket closeby. It all depends on which option is cost-effective for you. 

Spray the coils with the coil cleaning liquid, making sure to target the AC coils as much as possible. Wait for 10-20 minutes before rinsing the product off the coils. This will allow the coil to properly absorb the product, thereby causing the debris on the AC coils to dissolve into gunk.

Rinse off the gunk

A mobile source of clean running water like a hose must be used. This is important as you have to be careful to pour water on only the waterproof parts and avoid the electric parts of the unit and the cord of the air conditioning unit.

Wipe down the inside of the unit

Wipe the inside surface of the unit to remove all visible signs of mold. Use a bucket with diluted home detergent, with about 1/2 a cup of hot water. A sponge soaked in the bucket should be used to wipe the insides of the unit thoroughly. It is important to emphasize those hidden places that dust can easily settle in. 

Alternatively, you could use diluted bleach instead, but it is only necessary to do this if the unit has come in contact with bacteria-infested liquid like sewage.

Rinse off the filter

The air filter you soaked earlier should be ready in 45 minutes from the time you dipped it. It would help if you rinsed it with the hose to remove all the debris off it. 

Air-dry the parts of the unit

Somewhere with ample space should be used to carry this out, like your lawn. You should air dry for about a day before reassembling the unit and reinstalling it to its frame. If you leave it in a windy area or have windy weather at the moment, it will be better to air dry it using a fan indoors to prevent dust carried by the wind settling in it.

Precautions to take to prevent future mold growth.

Clean out your unit regularly

Mold spores are tough to get rid of completely because your air conditioner has many hard-to-reach spaces where these spores can settle. To prevent them from growing again, you must open up your air conditioning unit and vacuum it at least once a month. When you do this, you are robbing the mold of its food source.

Keep your AC running

Always keep your AC running even during the cold weather. The reason behind this is that it is harder for the mold to grow when the unit is running. However, you may worry about the cost of running it constantly, even when you don’t need it. 

Can You Use an Air Conditioner Without a Filter?

During those cooler months, the solution to this is to set the temperature to 10 to 15 degrees warmer than the temperature you would normally set. This is done to anticipate when the temperature will rise, so then the AC will not run as often, but it will occasionally cycle when the temperature in the house rises.


Mold growing in your air conditioner can be messy and difficult, so seeking professional help to know the scale of the problem is advisable. Sometimes the problem can be so overwhelming that you need professional cleaning to be done. Also, if the air conditioning unit proves to be too heavily infested, the best option will be to dispose of the unit completely. 


  • Vincent Steele

    Vincent is a freelance writer based in Santa Ana, California. When he isn't writing articles for Temperature Master, he can be found biking or hanging out with his cat, Shelly.

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