Can you just clean moldy ductwork or does it need to be replaced?

Hard sheet metal duct can usually be cleaned and treated. Flex duct or duct board with visible growth is harder to fully clean and is often replaced instead, especially in humid crawlspace or attic runs.

Should I turn off my AC if I think there's mold in the ducts?

Running the system can spread spores to other rooms, so many remediators recommend shutting it off (or at least closing off the affected zone) until the ducts are inspected.

Do I need an HVAC company or a mold remediation company for this?

Often both. The mold company handles cleaning, treatment, and containment; if duct sections or coils need physical replacement, that's typically HVAC contractor work coordinated alongside the remediation.

HVAC and air duct mold removal

Mold inside ductwork or on an air handler's coil is a different job from mold on a wall or ceiling, because the growth is actively circulating spores through every room the system serves. This is common in Charleston homes where AC systems run near-constantly through humid summers and condensation builds up around coils and drip pans.

Expect the technician to inspect the air handler, evaporator coil, drip pan, and accessible ductwork for growth, then clean or in some cases recommend duct replacement if flex duct or insulation is too contaminated to clean effectively. Sheet metal ducts can usually be cleaned and treated; some flex duct or duct board with heavy growth may need to be cut out and replaced rather than cleaned.

This is worth calling out separately from general remediation because it often requires coordination with an HVAC technician alongside the mold remediation crew, and because running the system during other remediation work can spread spores if the ducts aren't addressed first.

Signs to watch for: musty smell when the AC kicks on, visible growth around vents or the air handler, unexplained allergy symptoms that ease when away from home
Often needs: an HVAC tech alongside the remediation crew, especially if duct sections need replacing

What it costs

Cost depends on whether ducts can be cleaned in place versus needing sections replaced, the size of the system, and how many supply/return runs are affected. Homes with flex duct in a moldy crawlspace or attic often cost more since contaminated duct material typically gets replaced rather than cleaned.

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FAQ

Can you just clean moldy ductwork or does it need to be replaced?: Hard sheet metal duct can usually be cleaned and treated. Flex duct or duct board with visible growth is harder to fully clean and is often replaced instead, especially in humid crawlspace or attic runs.
Should I turn off my AC if I think there's mold in the ducts?: Running the system can spread spores to other rooms, so many remediators recommend shutting it off (or at least closing off the affected zone) until the ducts are inspected.
Do I need an HVAC company or a mold remediation company for this?: Often both. The mold company handles cleaning, treatment, and containment; if duct sections or coils need physical replacement, that's typically HVAC contractor work coordinated alongside the remediation.