Signs of Mold in Air Ducts

There may come a time when you suspect that there might be mold in your air ducts. This is a common problem, and there are many signs that can tell you when there is mold in your air ducts. This sounds intimidating and, when coupled with the fact that some signs require different treatments, can become overwhelming. Luckily, there’s no need to panic; we’re here to help.

In this article, we’ll not only inform you of the different signs that there is mold in your air ducts and how to handle them, but we’ll also explain what causes mold to form and the steps you can take to prevent it from happening.


For mold to grow, it needs a dark, warm, and moist environment. Your air ducts already provide warmth and darkness, so you must pay attention and watch for any dampness. First, run your AC unit to control the humidity levels inside the ducts. They are small, enclosed spaces, so heat and moisture can build up and stick around for quite a while if they’re not addressed. 

Another thing to watch for is your bathroom’s ventilation. If your bathroom cannot release steam correctly, it will begin to travel into the vents, providing the necessary moisture and temperature for growth. Another thing to watch for is leaks near the system or in the roof. If you suspect there’s a leak; it needs to be addressed immediately to prevent mold growth in the air ducts and also prevent both growth and damage in the home itself. 

The final thing to watch for is mold growth in your home. If a leak forms behind a wall or in the roof, or if another area becomes damp and is left alone for too long, mold can begin to grow there. The spores will then be circulated throughout the ducts and can cause a lot of other problems if left unaddressed. 

If you do find mold somewhere in your home, call in a professional mold removal team, such as Panhandle Cleaning & Restoration, and ask them to also test the ducts. If their tests come back positive, they can then return and clean your ducts as well.


You can prevent mold from growing in your ducts in a few ways. For one, check your roof in warm months after heavy rain and wind storms and after heavy snows, freezes, and ice events in cold months. Doing so will allow you to locate and repair damage as soon as it occurs, minimizing leakage and water damage. 

Another way is to use high-quality air filters and purifiers. These devices will either catch or neutralize any potential spores and dirt before they become a problem. Be sure to check and clean any filters regularly to ensure they continue working at peak efficiency and that they don’t start growing mold themselves. Also, check your HVAC system and air ducts regularly, and clean out drip pans. 

Drip pans can collect water, so removing and cleaning them before they can is a good idea. Checking your ducts for signs of mold and ensuring your HVAC system is running like it should and isn’t leaking is one of the best ways to prevent mold growth. Make sure to clean your vent covers every now and again as well, as they can collect and hold dirt themselves. Failing to take these steps can cause mold growth, which can be difficult and expensive to remove and can make you ill.


Even with all of these prevention measures, there may be a problem that you can’t see yet that could cause mold to grow in your air ducts, so it’s a good idea to watch for the following signs:

Illness or Increase in Allergy Symptoms

If you notice you or your family becoming sick more regularly or if there’s an increase in your allergy and asthma symptoms, then there might be mold growth in your ducts. 

This illness and symptom increase can be caused by the spores entering your body as you breathe, which then causes an allergic reaction to occur. The more mold there is, the worse the symptoms will be, so acting as quickly as possible is best.

Musty Smell

Sometimes, you may notice a smell when the HVAC system first kicks on. If you haven’t run the air conditioning or heating unit in a while due to the weather or season, you may notice a smell as it activates the first few times. 

This could simply be because the system has sat dormant for a while. However, if the smell is musty and lingers, there may be mold growth in your air ducts or HVAC system.

Visible Growth in HVAC or Ducts

This is the most obvious sign of mold growth. You may have mold if you notice black, white, or green spots around your HVAC system, vent covers, or inside your vents. If the spots are the right color, telling them apart from dents or dirt may be difficult, so pay close attention. If it looks like a part of your system is covered in polka dots, it’s a sign of mold growth. 

Your air ducts are dark, so simply peering through the cover at the ducts isn’t enough. You’ll need to remove the cover and shine a light into the ducts. If you see these polka-dot-like spots, then you have mold growth in your ducts.

Methods of Removal

To remove mold from your home, search for potential causes. This could be anything from a leaky pipe to a window with more condensation due to its location. Once problems are located, address them promptly. Failing to do so will result in more mold growth and could even cause other issues, such as water damage. Then, have a professional team come in and test your ducts. 
Should the test return positive, you need to hire a professional mold cleaning service to abate and remediate the situation. If you’re looking for one, contact the professionals at Panhandle Cleaning & Restoration. We have extensive experience with mold removal and water damage and can help you handle both issues.

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