Problem guide
How to clean air conditioner mold
Mold grows where dust meets moisture. Cleaning the surface is half the job; fixing the moisture is the other half.
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Written by HYRE HVAC Research Desk Primary-source research, data analysis and fact checking
The short answer
To clean air conditioner mold on a window unit, unplug it, remove and wash the filter, and wipe reachable surfaces with mild detergent and water, then dry them fully. On central systems, owners can clean supply registers and change the filter.
Mold on the evaporator coil, blower or inside ducts is a job for a technician.
EPA advises fixing the moisture source first, or the mold returns.
Safety first
Wear gloves and an N95 respirator, and keep the area ventilated. People with asthma, allergies or weakened immunity should not do the cleaning.
Unplug a window unit. For central systems, switch the system off at the thermostat and breaker before removing registers near the air handler.
Bleach mixed with ammonia or acids releases toxic gas. Plain detergent and water is the safest start.
Cleaning a window AC
Move it to a work area if you can do so safely.
Lukewarm water and mild detergent; let it dry fully. See cleaning a window AC filter.
Grille, front panel and visible plastic parts, with detergent and water on a cloth.
A soft brush and a no-rinse coil cleaner made for AC coils, following its label. Keep liquids away from electrical parts.
Run the fan-only mode for a while before cooling, or let it air dry.
What about central air?
Owners can remove supply registers and wash them, vacuum dust from the opening, and change the filter.
Mold on the evaporator coil, the drain pan or the blower wheel means opening the air handler cabinet near electrical parts; that is technician work.
EPA’s guidance on duct cleaning says to consider cleaning if there is substantial visible mold growth inside ducts or on other system parts, and to correct the moisture problem, or the growth will likely return.
EPA also says not to let a service provider apply biocides or sealants inside ducts without understanding the pros and cons.
Where mold comes from
| Source | Fix |
|---|---|
| Clogged condensate drain | Clear the drain; see AC leaking water |
| Oversized AC that short-cycles | Poor moisture removal; a technician can assess sizing |
| High indoor humidity | Dehumidify; a technician can check whether the AC removes enough moisture |
| Dirty filter and coil | Regular filter changes |
| Window unit stored wet | Dry before storing; run fan-only first |
When to call a professional
Cleaning means opening the cabinet near electrical parts.
Ask for a duct inspection; see air duct cleaning.
A hidden moisture source needs finding.
EPA guidance suggests professional help for large areas.
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Questions
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HYRE HVAC Research Desk
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