Mold in your ducts: warning signs and next steps
Musty smell when the AC turns on? Here's what to do — and what not to do.
That musty, damp-basement smell in the first thirty seconds of a cooling cycle is the most common sign of microbial growth inside a duct system.
Warning signs
A musty odor that appears only when the system runs.
Visible dark speckling on register slats or the first foot of duct.
Standing water or rust near the air handler drain pan.
Allergy or sinus symptoms that improve when you leave the house.
What not to do
Don't fog a household disinfectant into your returns, and don't scrub visible growth with a shop vac and brush — both spread spores through the whole system and skip the actual cause, which is moisture.
The right sequence
Find and fix the moisture source, clean with negative-pressure containment, then apply an EPA-registered antimicrobial. Ask for before-and-after photos of the interior duct surfaces.
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