5 Signs Of Mold In Air Ducts And How To Get Rid Of Them

HVAC air ducts can be an excellent host to a wealth of mold strains, some of which cause moderate to adverse health problems. Avoiding frequent maintenance of your air ducts can be detrimental to your health and that of your family.

If you’re wondering, ‘How can I tell if there is mold in my air ducts?’ here are 5 tell-tale signs, some invisible to the eye, that might indicate mold.

But first, let’s understand mold growth in air ducts.

What Triggers Mold Growth In Ductwork?

How Can I Tell If There Is Mold In My Air Ducts
Photo Credit: Depositphotos

Mold thrives in air ducts when warm temperatures and moisture are present. A warm, humid environment provides the most suitable conditions for mold to flourish. Poor ventilation traps moisture in the walls, causing condensation. As a result, mold forms on the ductwork. Here are some of the HVAC issues that may contribute to mold growth.

1. An Oversized AC Unit

HVAC outdoor unit
Photo Credit: Depositphotos

If you have a unit that’s too big for your home, mold is likely to grow in the ductwork. Bigger units can cool small spaces quickly and turn off before dehumidifying the air, causing excess moisture. This moisture buildup may result in mold growth. Before the installation, make sure to listen to professional advice on the HVAC unit that would be perfect for your home’s size.

2. Setting Your AC On Too Low Temperature

thermostat too low
Photo Credit: Depositphotos

When your HVAC is set at an overly low temperature, mold growth around the ductwork can occur. Cool air from the air ducts meets warm air in the room, and temperature differences may cause the moisture in the air to condense on the surfaces and around the ductwork.

If this moisture doesn’t get a chance to dry, it builds up and forms the perfect breeding ground for mold. The process is known as temperature differential and typically takes about a 20-degree difference to form moisture. If the moisture goes unnoticed for weeks or months, it inevitably makes its way into your air ducts.

3. Leaking Ducts

leaky ducts
Photo Credit: Depositphotos

If your ductwork leaks, warm air in the atmosphere may be seeping through, causing a temperature differential. The difference in the warm air in the walls can result in moisture condensation on the ducts, ushering in the perfect environment for mold growth.

What Are the Signs of Mold in my Air Ducts?

check for mold in air vents
Photo Credit: Depositphotos

While you can’t always see directly into your air ducts, these 5 signs can indicate mold growth. If you detect any of these signs, call your air duct cleaning professionals to service your air vents immediately.

1. A Musty Smell When Your HVAC Is On

what does musty smell from HVAC mean?
Photo Credit: Depositphotos

When there’s a large presence of mold, you’ll notice the unit emitting a pungent odor that can be described as earthy or musty. Although the smell might be unpleasant, the good news is that larger mold infestations are easier to detect.  

When you have mold buildup in your ductwork, the smell is typically strongest when the unit is running. That’s because the air that stems from your ducts will collect and carry more spores as the mold spreads. Spores will settle into the ducts when your system isn’t operating, making the odor harder to detect.

2. Visible Mold On Air Ducts

mold on air vents
Photo Credit: Depositphotos

Since air from your HVAC system travels through the vents before reaching your rooms, mold growth on vents isn’t uncommon. If you notice discoloration around vents, appearing as black, green, brown, or yellow spots, it’s a dead giveaway of mold. Even if you don’t notice mold outside your vents, you should occasionally remove them and examine them for mold growth on the side facing the duct.

3. Allergy Symptoms and Illness

allergies from mold
Photo Credit: Depositphotos

Mold can trigger allergy symptoms ranging from difficulty breathing, itchy, sneezing, and watery eyes to coughing. Breathing mold spores can result in confusion, fatigue, diarrhea, nausea, and vomiting in more chronic instances. If you notice these symptoms, stop using your HVAC unit and call a professional for a thorough inspection.

4. Mold In the Air Conditioner or Furnace

mold on ac
Photo Credit: Depositphotos

The most common places to notice mold in an air conditioner are the drain pan below it or the evaporator coils. These components are frequently coated with condensation that may provide adequate moisture for mold to thrive. You might notice mold anywhere on your furnace as it heats and humidifies the air in it. If you see mold growth on these appliances, there is a chance mold may have spread through the ductwork when your HVAC was running.

5. Mold In Other Areas Of The Home

mold in bathroom
Photo Credit: Virunja

Mold can thrive below the fridge, next to the motor area, on the bathroom walls and ceiling, below the bathroom sinks, and underneath the kitchen. That’s particularly true when the bathroom lacks a window, and the only ventilation source is a vent fan. Cross-contamination may occur if you have a mold problem in other parts of your home.

How To Get Rid of Mold On Air Vents

how to get rid of mold on air vents
Photo Credit: Depositphotos

To get rid of mold from a vent register and improve indoor air quality:

  1. Remove the vent cover and immerse it in water.
  2. Add laundry detergent.
  3. Let the vent cover soak.
  4. Vacuum the exposed ductwork to remove as much mold as you can from the duct system.
  5. Clean and let the vent cover dry thoroughly before re-installing it.

As a precaution, wear a face mask and gloves to minimize contact with mold.

How To Prevent Mold In The Future?

how to prevent mold in air vents
Photo Credit: Depositphotos

Once your air ducts have been cleaned, you need to keep up with regular maintenance at least once every 3 to 4 months to prevent mold. Replace the HVAC system filters, reduce condensation within the ducts by insulating them, clean your drip pans regularly, seal any condensation and leaks, purchase a good dehumidifier, and use it in areas more prone to mold growth.

AC Unit is Running, But No Air Is Coming Through The Vents. Why?

AC running but no air through vents
Photo Credit: Depositphotos

If your AC is running but no air is coming through the vents, there are so many reasons why this could be happening. Here’s how to do some basic HVAC troubleshooting before calling in the professionals.

How To Balance Air Conditioning Vents

balancing AC air flow
Photo Credit: Depositphotos

There’s no denying that air balancing will enhance the overall performance of your heating system, boost energy efficiency, and elevate air circulation. For most homeowners, that entails delivering just the right amount of cold or hot air to each room for optimum comfort. Here are our best tips for balancing air conditioning vents for comfort.