Is Mold in an Air Conditioner Dangerous?
The EPA says molds have the potential to cause health problems, producing allergens, irritants and, in some cases, potentially toxic substances called mycotoxins. The CDC says mold can get into a home through open doors, windows, vents, and heating and air conditioning systems.
Air conditioners create moisture. The EPA says research suggests condensation on or near the cooling coils of air conditioning units is a major factor in moisture contamination of the system, and advises not running the HVAC system if you know or suspect it is contaminated with mold, because it could spread mold throughout the building.
The EPA says to consider having air ducts cleaned if there is substantial visible mold growth inside hard surface ducts or on other components of the heating and cooling system, while noting that duct cleaning has never been shown to actually prevent health problems, and that studies do not conclusively show that dust levels in homes increase because of dirty air ducts.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Government sourceThe EPA says molds have the potential to cause health problems, producing allergens, irritants and in some cases potentially toxic substances called mycotoxins. US EPA ↗
- Government sourceThe EPA advises not running an HVAC system you know or suspect is contaminated with mold, because it could spread mold throughout the building. US EPA ↗
- Government sourceThe CDC says mold can get into a home through open doors, windows, vents, and heating and air conditioning systems. CDC ↗
- Government sourceThe EPA says research suggests condensation on or near the cooling coils of air conditioning units is a major factor in moisture contamination of the system. US EPA ↗
- Government sourceThe EPA says to consider cleaning air ducts if there is substantial visible mold growth inside hard surface ducts or on other components of the heating and cooling system. US EPA ↗
- Government sourceThe EPA says duct cleaning has never been shown to actually prevent health problems, and studies do not conclusively show dirty air ducts increase dust levels in homes. US EPA ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.