Signs You Have Mold in Your Central Air System (And What to Do About it)

Mold in your central air system can have negative effects on both your AC and your health. Check out these signs you have mold, and learn what to do about it.

Have you noticed an odd, moldy smell in your home, but you can't seem to pinpoint where it's coming from?

You've checked the refrigerator, the bathroom, and behind the washing machine, but you're still coming up empty. Maybe the culprit is actually your central air system.

The idea of having dangerous mold spreading throughout your home through the air vents can be nerve-wracking, but there are some simple signs that can tell you if that's the problem.

Keep reading to discover the signs and causes of mold in your central air system, and what you can do about it.

How Common is Mold, and What Causes it?

Mold in homes is more common than you may think.

According to a World Health Organization report, dampness and mold exist in 50% of American homes. More specifically, one out of every six allergy sufferers' symptoms can be blamed on mold in their central air system, according to a study done by the National Institutes of Health.

Even the smell of mold can be enough to cause illness, even if there aren't any spores present.

Now, you're probably asking what exactly causes mold?

Well, mold can grow as long as the following three factors are present: food, moisture, and a stable environment. Unfortunately, your central air system is the perfect home for mold.

Air conditioners work by taking air from the outdoors. This causes dust to build up in the ducts, which contains food for mold.

Moisture, in the form of condensation, also tends to form in units. This is especially true during warmer months or for those who live in humid areas. If you aren't running a dehumidifier, the risk of condensation is greater since excess moisture will be less likely to evaporate into the air.

Lastly, mold likes to grow in dark, undisturbed places. Since your central air system is stable and has no light shining through it, it becomes the perfect environment for pesky mold to make their home.

Now that we know what causes mold, here are some signs that you might have mold in your HVAC unit.

You Can Smell It

Yes, we all know that distinct smell of mold. If you start smelling it in every room of your home, then it could be caused by your central air system. A more tell-tale sign is if you notice that the smell gets worse when you try to turn on your air conditioner.

You Can See It

Check your air ducts, intake vents, and drip pans. Do you notice a patchy black residue? If so, that's another sign of mold in your central air system. Don't be fooled if it easily wipes away. More mold can be present throughout the ducts, and special cleaners are needed to effectively remove the mold to help ensure it doesn't grow back.

You're Feeling Sick

Mold can cause you and your family to experience some potentially dangerous health conditions. Coughing, wheezing, congestion, and irritated eyes, throat, or skin are among the symptoms that can be caused by mold in the home. Some people can even experience infections and respiratory illnesses that may require hospitalization.

So, now that you know how to identify the signs of mold, what do you do about it?

What To Do About Mold in Your Central Air System

While hiring a professional might be your best bet to ensure the job is done right, you can also take the steps to remove the mold in your central air system yourself.

Here are the six steps you should take to remove mold:

1) Choose the right cleaner. The EPA recommends a mixture of detergent and water, but several commercial mold removals are available as well.

2) Find the right protective gear. Gloves, eye goggles, and a mask are the essentials when dealing with mold. Those who are particularly sensitive to mold may want to consider investing in coveralls to ensure you won't be exposed to it during removal.

3) Spray the area with your chosen cleaner, and let it sit for a few minutes.

4) Scrub the area down until all the mold is gone. Remember: mold is persistent! The smallest amount of mold left behind can be enough to start a whole new colony. Every mold spore has to be gone for this to work! To prevent scratches in your ducts, avoid using anything abrasive, like a wire brush, and opt for rags or a scrub brush instead.

5) Dry the entire area. Either disinfect or dispose of anything you used to clean up the mold. If you choose to disinfect your equipment, make sure to be thorough because mold can be transferred from surface to surface.

6) Check back in the next few weeks. If you see signs of mold, then you may have to take some steps to further prevent mold. If it seems like your system is leaking, you may want to look into fixing or upgrading your system to avoid further problems.

Phew! Take a deep breath - the worst is over.

Once you have a mold-free home again, you'll probably want to take some preventative steps to ensure that it stays that way.

To prevent mold build-up in the future you should:

1) Replace your air filters every three months.

2) Insulate your air ducts to reduce condensation in your unit

3) Use a dehumidifier. If your unit does begin to accumulate condensation, a dehumidifier could help. If the air in your home isn't moist, the condensation will evaporate into the air instead of collecting in the unit.

4) Check and clean your drip pans regularly so water doesn't collect.

5) If you notice any wet areas, dry them immediately. Condensation, spills, and leaks can all cause water build-up which can lead to mold growth.

6) Have your ducts regularly inspected and cleaned by a professional.


Nobody likes mold in their homes. But once it has started to grow, it can be a process to remove.

Whether you remove the mold yourself or have a professional come in to do the dirty work, remember to prevent future mishaps by properly caring for your central air system.

Want to learn more about what you can do to improve the quality of your home? Check out the services we offer.

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