Why Your HVAC Smells Musty (And How To Fix It)
Musty smell from supply vents is almost always biological growth — mold, mildew, or biofilm — on the evaporator coil, in the condensate pan, or inside the duct liner.
Inspect the condensate pan
A clogged or sloped-wrong pan holds water that supports growth. Clearing the drain line is a 15-minute fix that solves a lot of musty smells.
Coil cleaning + UV-C
An annual non-acid coil clean plus a UV-C lamp aimed at the coil keeps biological growth off the wet surface year-round.
Replace flex duct that's contaminated
Internally lined ducts that show visible growth can't be sanitized — they need to be replaced.
Frequently asked questions
- Is a musty smell dangerous?
- It indicates microbial growth that can aggravate asthma and allergies. Treat it.
- Does ozone fix it?
- Temporarily. Without addressing the moisture source it returns.
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