7 Possible Symptoms of Mold in Your Air Ducts

Becca Stokes
Written by Becca Stokes
Updated November 12, 2021
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Mold in your air ducts is nothing to sneeze at

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If itchy, watery eyes and constant sneezing are making it hard to binge your favorite shows, it’s time to find the culprit. Could it be the dog, seasonal allergies, or something else entirely? Learn the symptoms of mold in your air ducts so you can resolve this issue and get back to watching television in peace.

What Is Mold?

Black and white interior of luxury living room
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Mold, it’s not just green stuff on that loaf of bread you forgot on top of the fridge. Mold is a living thing (a fungus). Mold gets bigger and sustains itself by “eating” veggie and animal matter and then ejecting spores that travel through the air. 

When you’re outside, being around mold isn’t really an issue. But when you’re indoors and invisible spores can move about, that’s a different story. But don’t worry. Unless your HVAC system is older, mold in your air ducts shouldn’t be an issue.

7 Physical Symptoms of Mold in Your Air Ducts

Whether you’re allergic to a certain type of flower or mold, you might experience similar symptoms. 

Here’s a look at seven possible physical symptoms that can arise from mold in your air ducts:

  • Wheezing

  • Stuffy/runny nose

  • Rashes

  • Hives

  • Itchy/red/watery eyes

  • Asthma

  • Other respiratory problems

People with asthma are particularly susceptible to mold spore allergies. If you or someone living in your home has recently developed symptoms like those above, and seasonal allergies and illness have been ruled out, it could be from mold in your air ducts. 

However, since everything from the tree in your backyard to the mold in your air ducts can cause itchy eyes and hives, it’s important not to jump to the worst-case scenario. Hire an HVAC contractor to confirm if you have mold, and have your unit and vents cleaned to see if it remedies the issue.

How Mold Spreads Through Air Ducts

Mold relies on its spores to travel, spread, and grow. Because the spores themselves are so lightweight, the air moving through your home’s HVAC system can often move them around without your knowledge. 

Those spores can grow into mold inside your air ducts if moisture settles inside of them. Mold prefers wet, cool environments, and moist air ducts are a popular place for them to set up shop. After these spores have settled, all it takes is a gust of air from your ducts (be it hot or cold air) to send that mold into the air you breathe at home.

Air Duct Parts Most Sensitive to Mold

While your entire HVAC system can be affected by mold, there are certain components that are more likely to breed mold and mold spores:

Air Intakes

The intake component of your HVAC system is sensitive to mold because of its proximity to water and to debris like decomposing leaves. Keeping the intake area clean and dry can help reduce the conditions that mold loves so much.

Internal AC Components

Your air conditioning is going to have a lot of moisture, particularly if you live in a more humid environment. The humidification systems, cooling coils, and drain pan are common places for mold to spread.

How to Test for Mold in Your Air Ducts

If you suspect you have mold in your air ducts, the first thing you need to do is have that suspicion confirmed and the second thing you need to do is get rid of the mold in your home

Luckily, a qualified HVAC service provider in your area can tackle both. While some mold (black and white mold) may be visible to the human eye, that’s not always the case, particularly with spores. 

DIY mold testing kits are available, but for a thorough evaluation, bring in a pro to do a mold inspection in your home.

How to Remove Mold From Your Air Ducts

Since mold removal involves chemicals, it’s best left to the pros. But if you decide to tackle it yourself, expect to follow these steps:

1. Wear Safety Gear

Make sure you wear a mask (N95 is highly rated). It will protect you from the mold and from the chemicals you’re using to treat the mold. Make sure your skin is covered, and always use sturdy work gloves.

2. Turn Your HVAC System Off

You can’t do any work on your air ducts unless your entire HVAC system is turned off.

3. Clean Air Ducts

Once you have the HVAC system turned off, use a mixture of equal parts water and baking soda to clean out your moldy vents. You can also use an Environmental Protection Agency (EPA)-approved mold-killing product or bleach. The severity of the situation will dictate what product will work the best.

4. Apply Mold Inhibitor

After cleaning the ducts, apply an EPA-approved mold inhibitor to prevent the mold from coming back.

HVAC Mold Prevention Tips

Once the mold is gone, get in the habit of scheduling annual inspections of your HVAC system. This isn’t just good for the lifespan of the heating and cooling system—it’s a chance for the pro to get their eyes on any mold that may have cropped up since their last visit. 

Getting rid of mold altogether is virtually impossible because the spores are microscopic. That said, you can stay on top of how much mold is living and breeding inside of your HVAC system.

Keep Your Air Ducts Clean

Clean your ducts whenever you spot mold on the outside. Take that as your cue to assume there’s mold inside as well and hire a pro to handle the job.

Manage Humidity Levels

Another way to reduce the amount of mold and mold spores moving throughout your home’s HVAC system is to manage the humidity inside your home. The less humid your home is, the less pleasant an environment the mold will find it to be. Try to keep humidity below 50% for ideal mold-banishing conditions.

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