Common Questions
Can mold grow in my air conditioner or ducts?
Answer
Yes. Air-conditioning systems handle a lot of moisture, and EPA lists condensate drain pans, porous liners inside ductwork and similar spots among the common places for hidden mold. A contaminated system can spread spores through the house, so EPA says not to run an HVAC system you know or suspect is contaminated.
Ducts don't need routine cleaning; the IICRC S520 says moldy duct liner, duct board or flex duct that can't be cleaned should be removed and replaced, and HVAC antimicrobials must be specifically registered for HVAC use. Keeping the drip pan clean and draining and indoor humidity below 60% are the main preventions.
What the sources say
“Do not run the HVAC system if you know or suspect that it is contaminated with mold.”
“condensate drain pans inside air handling units, porous thermal or acoustic liners inside ductwork”
“Keep heating, ventilation, and air conditioning (HVAC) drip pans clean, flowing properly, and unobstructed.”
“HVAC components (e.g., internal ductwork insulation, duct board or flexible ductwork) that have Condition 3 contamination and are made of materials that cannot be successfully remediated, should be removed”