Moldy Air Ducts: How to Detect Them and What to Do

In the Florida heat, when you hear the air conditioner turn on it is to be a welcome relief. However, have you ever been in a building where you’re met with an irritating musty smell? This is often a sign of a much-needed air duct cleaning due to mold in the ducts. Before you call your HVAC specialist for a duct cleaning, it’s important to understand the problem and know the culprit.

How to Tell if Mold is in Your Air Ducts

Heat and humidity make residential and commercial buildings in the North Central Florida region a haven for growing mold. Your heating and air conditioning system creates a prime environment for mold and mildew with increased moisture. Be on the lookout for these signs of mold year-round.

Visible Mold

Mold grows best in the dark corners of your home or business. While you should take an initial look at your air vent from the outside, with some digging you can spot mold’s favorite hiding places. Open up your air vent, the air ducts, condenser coils, and drip pans to inspect the areas with a flashlight.

To go one step further, check for moisture build-ups in these areas to see if they are a welcoming environment for mold. Use a dry, white cloth or paper towel to dab at these areas. If the cloth or paper towel comes back wet, this is a prime spot for mold and mildew to grow if it isn’t already there.


The most prevalent sign of mold in your air ducts is a musty smell of mold or mildew when your HVAC unit is on and running. You will notice it most when your unit first turns on and are directly downstream of the air vent. This odor creeps into other rooms and areas of your space, not just around the vents. Over time, this smell gets into your furniture, clothes, and more. 

Mysterious Symptoms

Prolonged exposure to mold and mildew breathing in high concentrations of particles leads to dangerous symptoms for humans. These can present themselves in mysterious allergy-like symptoms such as headaches, dry/runny nose, sore throat, eye irritation, or even skin rashes. If you face any of these symptoms while inside your home and they go away once outdoors, it is likely due to mold growth in your air ducts.

Seek medical attention for severe symptoms and make sure to eliminate mold growth as soon as possible. Continual exposure to moldy air ducts may have long term health consequences on your respiratory and immune system.

What to Do About Mold in Your Air Ducts?

Once you find mold in your air duct, it’s important to address the problem as soon as possible. There are some homemade recipes for cleaning mold including mixtures of bleach and water or baking soda, detergent, and other household products. However, if you want to stop mold in the long term from coming back, there are a few preventive steps you can take for your home or office as well.

  • Keep Steady Temperatures – Major swings in your temperature promote moisture buildup. If you let your home get to 79 degrees, then turn on the AC to 67 degrees, the warm air meeting the cool air around your vents and ducts creates high levels of condensation.
  • Check Unit Sizing – Check to make sure your unit is properly sized for your space. If you’re encountering mold, your unit may be too large for the airspace. When an oversized unit air-conditions a small space, it works too quickly and does not remove the humidity as desired.

Outside of these preventive measures and some initial cleaning, it’s important to make sure that you have your air ducts properly cleaned by professionals. Often, household cleaning solutions do not eliminate the problem as they do not reach every part of the air duct. 

Professional Air Duct Cleaning

Stellar Services is proud to offer a full suite of HVAC services to keep your home clean and comfortable. Our air duct cleaning services examine every aspect of your unit to make sure it is clean for the long run. Get in touch with us to keep your home happy and healthy all year long with an air duct cleaning.