Every time the AC kicks on, you get a wet-basement or dirty-laundry smell wafting through the vents. It's not your imagination.
You probably came here because…
- Musty or wet-basement smell when the AC starts
- Smell may fade after a few minutes of running
- Worse in humid weather
- You may have allergy-like symptoms indoors that go away outside
What’s actually happening
This smell is almost always microbial – mold or mildew growing somewhere the AC is producing condensation. Three usual suspects: the evaporator coil, the drain pan, or damp spots inside the ductwork.
The evaporator coil is the most common. It's cold, wet, and dark – perfect for microbial growth. Once biofilm forms on the coil, every time air passes over it, you smell it.
Drain pans can grow algae. Wet ductwork insulation from a past leak can grow mold. All fixable, but you need to find the source, not just spray an air freshener.
What we do about it
Change the filter to a higher MERV rating
MERV 11-13 catches more spores and reduces what circulates. Not a fix by itself but helps immediately.
Treat the drain pan and line
Pour a cup of white vinegar into the condensate cleanout tee every month. Kills algae and biofilm in the drain path. Add algae tablets to the pan if it has a holder.
Get the coil cleaned
This is the real fix. A tech pulls the coil access panel, cleans the coil with a professional coil cleaner, cleans the drain pan, and flushes the drain line. About $200-300 depending on access. Solves the smell 90% of the time.
When to just call
If the smell is strong, if you or family members have allergy symptoms indoors, or if you can see visible mold at the vents or coil, get us out. UV lights inside the ductwork can prevent it from coming back. Call (423) 637-1846.
Ready to fix it?
Call the family that’s been doing this in the Sequatchie Valley since 1996.