Air Conditioner Mold

Air conditioner mold hidden inside coil

Air conditioner mold contributes to unhealthy mold symptoms in virtually every home I investigate. In this post, I’m going to focus on the problems associated with window and wall air conditioners. These air conditioners are typically found in older homes, apartment and condominium buildings, and in hotel rooms.

I’ve had clients suffer asthma attacks and be rushed to emergency rooms due to hidden air conditioner mold. Unless someone has a very smelly air conditioner, most homeowners are unaware of hidden air conditioner mold affecting their indoor air quality.

Black mold and white mold

Air conditioner mold on vent register cover

Mold in window air conditioner grills is common. The photo above shows both black mold and white mold growing on the louvers on the front grill of a window air conditioner. Typically, air conditioner mold is not this blatantly visible. I enhance these photos to make it easier for you to see the mold. More often you have to inspect very carefully with a good flashlight to see it.

Air conditioners cool our air and simultaneously pull moisture out of the air so it doesn’t feel so humid indoors. What many people don’t realize is that because the units circulate air, they also collect microscopic particles that provide food for mold. The dust particles consist primarily of dead skin cells sloughed off of humans. Combined with the moisture in the air, the particles make it easy for air conditioner mold to germinate within the dust and extract nutrients from it.

Air conditioner mold hides inside ducts

Air conditioner mold hiding inside blower duct

Mold hid inside of the air circulating ducts of wall and window air conditioners also grows as a result of the nutrient-rich particles sticking to the cool damp surfaces inside. An interior mold inspection should be performed at least once per cooling season and more frequently if an air conditioner is used all year long.

Inspect your filter

I frequently discover mold in window air conditioner filters, filters that are plugged with dirt, and filters that are missing altogether. Clogged filters will ultimately cause mold to grow in the filters and on the cooling coils, as well as increase electrical usage.

air conditioner mold within dust on coil

The photo above shows mold in air conditioner coils that is growing as a result of operating the air conditioner without a filter in place.

Air conditioner filter media

If you don’t have a filter, you can either purchase one from the manufacturer or purchase a roll of air conditioner filter media from a local hardware store, as shown in the photo above. The media can easily be cut to size with scissors to fit most standard air conditioners.

Air condition mold and dust in filter media

The photo above shows a plugged filter being lifted up from behind the front grill. Behind the grill is where the filters are always located. Proprietary filters usually have plastic frames on them and will slide in from the top, sides, or bottom.

Filters should be inspected every 30 days. Depending on the air conditioner design, the filters either need to be removed and washed, or replaced.

Air conditioner mold hides in the condensate drain pan

Air conditioner mold and bacteria hidden in the drain pan

When installing wall and window air conditioners, some are not pitched correctly downward to safely allow water in the condensation collection pans to drain to the outdoors. Additionally, due to lack of maintenance, the drain holes in the water collection pans located underneath these air conditioners can also become plugged with bacterial growth.

In either of these instances, water can back up and leak into walls resulting in additional mold growth. Moreover, one of the bacteria that grows in water collection pans is Legionella. This is the bacterium responsible for legionellosis, a progressive and potentially fatal pneumonia, i.e. legionnaire’s disease.

air conditioner mold in the bedroom wall of a new condominium revealed with infrared thermal image

The photograph above is an infrared thermal image of an air conditioner in a bedroom wall in a new condominium building. The blue color below the air conditioner shows how the incorrectly installed unit has been leaking the condensate drain water directly into the wall system below. Water in the exterior wall insulation causes yet another mold contamination concern.

air conditioner mold caused from rain leaking into an exterior wall around the unit

The photo above shows an air conditioner in the window of an older home with pillows filling the openings on the sides of the air conditioner. The peeling paint on the windowsill is evidence of both drain pan and rainwater entering the exterior wall system below the air conditioner.

DIY Mold Inspection

If you see visible mold, detect a musty smell, or have reason to suspect a possible mold problem in your home, I recommend reading the Do-It-Yourself Mold Inspection series from If experiencing mold symptoms such as sinus infection, headaches, migraines, ADD and ADHD, asthma symptoms, memory loss, insomnia, respiratory disorders, or allergies, you have an additional reason to learn how to properly inspect your home for mold.

DIY Mold Inspection book

In this series you can learn how to perform your own mold inspection without the cost of hiring a mold remediation company, spending money on mold testing, or risk a common mold scam.

I’ll walk you through every room in your home, including the attic, garage, and basement/crawlspace. Using inspection photos with explanations, I’ll show you why and where to inspect for mold, and how to see hidden mold when it’s the same or similar colors as the surfaces it grows on.

Once you learn the methods of proper mold inspection, you’ll likely find black mold, white mold, and other colors of mold growing in a variety of locations around your home. This mold affects your indoor air quality and puts you at risk of unhealthy mold symptoms.

Don’t waste your money on mold testing

I often get calls from clients wanting me to do black mold testing, With a good conscience, I try to talk people out of paying me to do this.

Microscope for mold testing

Mold testing is largely a waste of money. Knowing the species of molds you have in your home is typically useless information. Your goal should be to find ALL areas of mold growth and safely eliminate them from your indoor environment.

Similarly, while air filters and air purifiers can significantly improve indoor air quality in mold-contaminated homes, they are NOT a substitute for a mold inspection.

You could easily spend hundreds (or thousands) of dollars purchasing products, testing for mold, or hiring professionals to look at your home, and still risk becoming a victim of incorrect information or buying devices that will not solve your problems. Wouldn’t you rather have the exact information you need, in layman’s terms, in books that are only $7.99?

Mold Remediation

Whenever mold is discovered, before proceeding with DIY mold remediation or hiring a professional mold removal company, the responsible thing to do is to become familiar with proper and improper methods of mold cleaning. You can do this by reading the book Do-It-Yourself Mold Cleaning and Prevention.

DIY Mold Cleaning and Prevention book

In this book I’ll teach you how to:

  • make your own mold remover solutions
  • protect yourself from mold exposure while performing mold removal
  • prevent mold spores from spreading further around your home
  • avoid being scammed by mold companies should you need one
  • prevent mold from returning

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