What Causes Musty Smell in Air Ducts?

Every time you switch on the AC, a musty odor bothers you. The musty smell is commonly instigated by mold or mildew growth in dirty air ducts. The smell no only irritates but may aggravate health problems and allergies at your home.

But what could be the possible reasons of the musty smell? Let’s try to find out –

Mold – Presence of mold and mildew in air ducts is the most common cause of the musty smell in air ducts. Mold grow when the following four conditions are met-
1. Food (dust or dirt)
2. Darkness
3. Moisture/humidity
4. Warm temperature

Dirty air coils are one of the most common breeding grounds of molds as they are located in the dark area and warm air constantly flows in the coil causing condensation over the coils. Dust and debris keep accumulating on the air ducts. All this results in mold and mildew growth. Regularly cleaning the air duct and by changing air filter on time reduces the chances of mold growth.


  • Install a UV germicidal lamp which will prevent the growth of mold.
  • Call professional air duct cleaners to clean dirty air ducts. Induct Clean team has more than 18 years of experience in air duct cleaning.

Leaky Air Ducts
• AC running for a long time but not cooling your home as needed
• Indoor air gets dirty and humid

Air ducts carry air to every part of your home. In case the air duct is leaky on its way it may draw in the outside air which is generally filled with dirt and spores. The dirty air inside can cause mold growth in the duct leading to musty smell.

Solution – You need to find the leaks and apply duct sealant to eliminate it.

More reasons of Musty Smell in Air Ducts

Clogged Air Filters – Clogged air filters mean reduced air flow leading the moisture to settle down in return air ducts. Moisture results in mold and mildew growth and that nasty smell.

Clogged Condensate Drain – Condensate throw extra water outdoor from the air handler. Blocked condensate drain results in moist duct resulting in mold and mildew growth and that musty smell.

Incorrect Fan Speed – Fan speed not set accurately cause result in the accumulation of moisture in air ducts setting conditions for mold and mildew growth.

Contact Induct clean for any query related to air duct cleaning, vent cleaning, carpet cleaning or other cleaning need at your home or office.
We operate in Philadelphia, South Jersey and Tri-State area and just a call away!

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