Do You Have Mold in Your Air Conditioner? Check for These Signs

These telltale signs can help you determine if mold is lurking in your air conditioner.

Mold is a common problem in warm, moist areas that don't get a lot of light. Unfortunately, your air conditioner can turn into a prime target for mold growth if it is not properly maintained. Organic matter from airborne dust and dirt can build up in the filter, giving mold the material it needs to breed. Luckily, you can prevent mold from settling into your air conditioner by cleaning or replacing the filter regularly.

If your air conditioner hasn't been used in several months or you keep smelling a musty scent when it's turned on, it's a good idea to inspect it to determine if mold is growing in the unit. Use this guide to learn common signs of mold growth, how to check for mold, and what to do if you find mold growing in your air conditioner.

Cleaning the air conditioner filter
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Common Signs of Mold in Your Air Conditioner

There are several common signs to look for when it comes to mold growth in an air conditioner. One of the most noticeable signs is a musty scent that only seems to fill the room when the air conditioner is running. This odor stems from mildew. The smell might be limited to a single room if you're using a window-mounted, freestanding, or wall-mounted air conditioner, but the musty scent can fully permeate your home if you have significant mold buildup in your central AC unit.

Mold is also known to cause a variety of negative health conditions, like allergic reactions, trouble breathing, and various respiratory problems. Signs of ongoing allergic reaction or respiratory problems can indicate the presence of mold. You can also see large patches of mold, so if you spot fuzzy, black, or green-black patches, you know the AC unit has mold. Mold can also be brown, green, white, pink, yellow, or orange, though black is the most common color.

How to Check for Mold in Your Air Conditioner

If a lingering musty smell or ongoing allergic reactions have tipped you off to the presence of mold, the next step is to inspect the air conditioner to verify that you have a mold problem. You can inspect a small window-mounted, freestanding, or wall-mounted unit by unplugging the unit and removing the front or back grill to access the filter.

Pull the filter out and visually inspect it for brown, black, or greenish stains that might look fuzzy. If the filter doesn't show any signs of mold, grab a flashlight, and inspect the inside of the unit. Mildew can also produce a powdery gray or white stain.

If you have a central AC unit, this process is more difficult because the bulk of the appliance is largely inaccessible. You can use a flashlight to inspect the supply vents, air ducts, fan, and exterior AC unit for signs of mold buildup. For a more thorough inspection, you will need to hire a professional HVAC maintenance company.

What to Do If You Have Mold in Your Air Conditioner

Finding mold in your air conditioner is a problem that you should deal with immediately. If the mold is heavily infesting a small air conditioner, it's recommended to replace the unit with a new air conditioner because even with significant cleaning there is a high chance that the mold will continue to thrive in unseen areas of the appliance. However, if the mold is relatively light, then you might be able to get rid of it before it spreads throughout the AC unit.

Wear safety glasses, a face mask, and gloves, then move the unit to a space where it can be cleaned without contaminating the rest of the home, such as the driveway. Open the air conditioner and remove the filter. You can either replace the old filter if it is disposable or wash the filter in a mix of 1 part liquid bleach to 10 parts water, allowing it to soak for at least 10 minutes to kill any mold.

Rinse the filter and allow it to air dry. While the filter dries, deep-clean all affected surfaces of the air conditioner with the solution of bleach and water. Rinse off the AC unit, being careful not to soak any electrical components, and allow it to dry before reinstalling the filter.

When to Contact a Professional

Dealing with a small infestation of mold in a window-mounted, freestanding, or wall-mounted AC unit is typically manageable for a DIYer, but if you have a central air conditioning system, it's recommended to call a professional HVAC maintenance service. Trained professionals who deal with these situations on a regular basis can gain access to all affected parts of the system and treat the problem directly without damaging the central AC, air ducts, or vents.

In some cases, it might be beneficial to look for an HVAC company that contracts yearly maintenance so that you know the system is always clean and up to date. This also saves you the trouble of tackling maintenance projects on your own, like changing the furnace filter or cleaning the air ducts.

How to Prevent Mold in Your AC Unit

Beyond professional maintenance, you can take steps to help prevent mold growth in your home and in your AC unit. One method is to reduce moisture buildup in the AC unit by regularly emptying the collection reservoir or investing in an air conditioner with humidity control. You can also prevent mold growth by cleaning the unit at least once a week and checking the filter.

Replace disposable filters about once a month or as recommended by the manufacturer. If you have a reusable filter, make sure to clean it once a month. Additionally, running the air conditioner can reduce mold buildup because the constant flow of air prevents mold spores from settling on the surface.

If you don't want your air conditioner running constantly, increase the temperature instead of turning it off completely. This will allow the AC to turn on intermittently, reducing the chance of mold settling inside the machine.

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