Mold has a tendency to grow in even the most unlikely of places in your home. If it’s not on your bathroom or basement walls, you might just find it in your air conditioner.

While this shouldn’t catch you by surprise, it should be a big reason for you to be alarmed. This is because mold and its spores in your AC means that you and your family are breathing contaminated air.

It might be the reason why you’re experiencing heightened allergic reactions or increased respiratory issues.

Mold in Air Conditioner How to Find, Fix & Prevent

Mold thrives wherever there’s some moisture, a source of nutrients, and warm temperature. In the air conditioner, moisture comes from condensation, or leakage in the coils.

The source of nutrients refers to the surfaces where the mold spores can settle and reproduce.

With most air conditioners and air ducts made from sheet metal, it’s usually harder for molds to grow in the air ducts. But once dust accumulates in your air conditioner, it becomes a good surface for mold spores to grow on.

Some factors that provide ample conditions for mold to thrive in your AC include:

  • Over-sized systems – An oversized air conditioner may cool your home quickly, but it poses an excessive moisture problem. Being too big for your home, it’s likely to turn off too early before dehumidifying the air. This leaves a lot of moisture in the air ducts.
  • Setting AC on very low temperature – If your AC is set under very low temperatures, it’s likely to result in condensation when the cold AC air meets the warm temperatures in the room. This promotes mold spore growth. The same happens if your air ducts have leaks allowing warm air to the vents.

What are the signs my AC has mold?

The only good thing with molds is that they’re very easy to detect. If you can’t see them, you can smell them, or feel them. Among the most conspicuous signs that your AC has mold includes:

  • Strong Musty smell when AC is on (or off)
    One of the key distinctive features of mold is its strong earthy-musty smell. This scent is usually strongest when the AC is on, and in rooms with massive mold infestation. In severe breakouts, the smell is also evident when the AC is off. This pungent smell is usually an indication that the mold is spreading.
  • Visible dark mold patches
    In the most affected areas, you’re likely to see several dark patches all around the vent. You might also spot them on the air ducts or the drip pans. By this time, the infestation rate is relatively high, and you might need a professional’s help to clean the mold. It’s important to note that different types of mold will be different in color. So, your mold patches could be green, black, yellow, etc., depending on the type of mold in your home.
  • Unexplainable symptoms
    Breathing in mold-contaminated air has numerous effects on your health. Some people experience common allergic reactions like sneezing, coughing, and wheezing, while others experience severe headaches, fevers, and nausea. For people with underlying respiratory problems, their conditions may suddenly start to worsen.

How to remove mold from air conditioner

Once you’ve confirmed that there’s mold in air conditioner, you need to work on eliminating them immediately. Cleaning out mold from your air conditioner, whether window AC, central Ac, or car AC is quite easy.

However, mold affects different AC units differently, and so; the remediation process may slightly differ. For instance;

Window AC: Mold spreads quickly on this unit since it’s harder to spot it on the air direction vanes. In most cases, most components of the AC are usually infested, making the cleaning harder. Experts usually recommend replacing the infested units.

Central AC: Unlike the window AC, mold infestations on the central AC spread throughout the entire house very quickly. Since it’s connected to the air ducts and heating system, replacing the AC won’t work, you’ll need to seek professional help.

Car AC: Molds can also find their way to your car AC if they’re exposed to flood or rainwater. Cleaning the mold is much easier, as you’ll only need to scrub it off with household cleaners. In extreme infestations, you can choose to replace the affected ducts. Some drivers also use different chemicals to kill the mold.

FAQ’s set up air conditioner

Steps to get rid of mold

Step 1. Put on protective gear – Before cleaning any mold-infested surface, protect yourself with the right supplies. You’ll need a facemask, eye protection gear, and gloves.

Step 2. Turn off the AC and ensure it’s not connected to a power source.

Step 3. Open up the AC grills (you may need a screwdriver) and find the air filters. Clean the filters or replace them when possible. If it’s washable, use the laundry detergent with hot water and a scrub brush to wash it clean.

Step 4. Take a vacuum cleaner and go back and unscrew the cover that’s usually behind the filter. Now vacuum all the debris and dirt in this area. You might also notice some mold here – try to wipe it clean.

Step 5. Mix some bleach with water, wet a sponge or cloth with the solution, and then use it to scrub the AC evaporation coils, ducts, and other surfaces. You can also put the solution in a spray bottle and spread the solution throughout the moldy areas of the AC unit. Let it sit there for around 15 minutes.

Step 6. Finally, rinse the AC components with a clean cloth and let them dry, then reassemble the AC and plug it back to a power source.

Tools & Safety equipment needed

To successfully remove molds from your AC, you’ll need the following supplies:

  • Bleach
  • Laundry detergent
  • Scrub brush
  • Gloves
  • Eye protection gear
  • Face mask
  • Vacuum cleaner
  • Water
  • Cloth
  • Screwdrivers
  • 5-gallon water bucket

How to prevent mold returning to air conditioner and ducts

After a successful mold remediation and cleaning project, the next huddle is ensuring the mold never finds its way back to your AC again. According to the US Environment Protection Agency (EPA), the best way to prevent mold growth is by controlling your moisture.

There are many ways homeowners can do this. Some of the most effective methods include:

Having a regular cleaning plan – Regular AC inspection and cleaning allows you to spot mold infestation early enough to prevent an infestation. It also helps you identify faulty components like duct leaks that could result in mold growth.

Keep the AC filters, grills, and ducts clean and dry at all times to prevent dust build-up on the surfaces.

Get a dehumidifier – If you’re in an area with high humidity, consider getting an air dehumidifier. Dehumidifiers eliminate excess moisture from the air, ensuring the conditions aren’t right for mold growth. In the bathroom and kitchen, you can also consider improving the ventilation.

Monitor your plumbing system – leaks in your home’s plumbing system could easily be dripping water droplets to your AC system. Ensure all plumbing is in the best state.

Close windows and doors when AC is running – Open doors and windows not only beat the point of having your AC on, it also increases the amount of humid air entering the home and hence leads to condensation – which is a mold-magnet.

Install Ultraviolet lamps near the affected areas – UV light is scientifically proven to kill and prevent any mold growth in your AC. The light also kills other viruses and bacteria that might be found in your system.

Bottom Line; Getting a professional to regularly inspect your AC units is always the best way to prevent mold from coming back. An expert can easily detect signs of a mold infestation before you can!

How to prevent mold returning to air conditioner and ducts cleaning

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AC coils are common culprits for collecting dirt and debris that attracts mold growth. To clean it, you first need to establish a schedule. Depending on the state of your coils, you can opt for a monthly or seasonal coil cleaning schedule.

Next, determine the method you’ll use to clean the coils. Some homeowners use compressed air, others commercial cleaners, others detergent and water, and others heavy-duty cleaning.

  • Cleaning using compressed air
    First, open the AC unit and direct compressed air from the clean side of the coil to the dirty side. To prevent damaging the fins, direct the air at 90-degree angles under high-pressure.
    With consistent flow of air, any dust build-up will be displaced and blown away. However, avoid blowing the debris towards the AC ductworks or your house.
  • Cleaning using a brush
    In cases of minor dirt accumulation, simply brush away the dirt from the affected coils. Just ensure that the brush bristles aren’t too hard to ensure they don’t damage the AC fins.
  • Cleaning using detergent and water
    This method requires a mild detergent and some warm water. First, mix the detergent with water to form a solution and then pour it into a spray bottle.
    Spray the solution onto the dirty coils, then leave it to soak for a few minutes. Finally, use a soft-pad brush or cloth to wipe away the loosened debris.
  • Cleaning with commercial cleaners
    If detergent and warm water doesn’t work, commercial cleaners can be a great alternative. First, choose an EPA-approved cleaner, then read the product’s terms of use.
    Next, depending on the instructions of your chosen cleaner, apply it on the dirty coils and give it some time to foam and loosen the debris. Repeat this process until all debris breaks away, then use a cloth to wipe dry the coils.
  • Heavy-duty coils cleaning
    This method only applies to extremely dirty coils. It involves using pressurized water, strong commercial cleaners, and even steam cleaners.

You’ll first have to remove or disintegrate the heavily affected parts, apply the cleaners and rinse them under pressurized water.

Keep in mind; Hiring a professional cleaner for this task is always recommended to avoid damaging the AC unit.

When you’re not sure whether those dark patches you see on your AC are molds, a mold test can give you a pretty conclusive result.

To test for molds, you’ll first have to understand the three types of tests; air testing, surface testing, and bulk testing. Air testing tests the concentration of mold spores in your home.

Surface testing analyses household materials in your home to find the extent of mold growth. Bulk tests take materials from your house and test them to find the concentration of mold in the house.

For your AC, you’ll have to conduct both an air test and surface test of your AC coils and filters to determine if they are mold-infested.

There are several ways to do this. The easiest way is by cleaning your air ducts, vents, and filters with a bleach solution. Bleaching products with sodium hypochlorite ingredients eliminate the mold and gets rid of their smell. You should also clean and replace your air filters.

If the smell persists after cleaning, your entire AC system may need full cleaning, and that’s a job for professional cleaners.

Important: Always put on your protective gear (gloves, face mask, eye gear) when handling bleach.

Yes! The Centre for Disease Control (CDC) has put out several warnings regarding the dangerous impacts of using an AC with molds. The most common effects of mold affect people with chronic respiratory problems such as asthma and lung disease!

You’re also likely to develop numerous allergic reactions to the mold, including eye, throat, and skin irritation, coughing, headaches, wheezing, and nasal stuffiness.

Timothy Munene
Author: Timothy Munene - Timothy is a freelance writer and an online entrepreneur.