Why Does My AC Smell Musty?

A musty smell from the AC often points to moisture somewhere in or around the HVAC system. Don't cover the smell with fragrance and assume the problem is solved.

When do you smell it?

Notice whether the odor appears only when the AC starts, continuously while it runs, in one room, or throughout the house.

Moisture deserves attention

Cooling systems remove moisture from indoor air. Problems involving condensate, drainage, wet materials, or excess indoor humidity can contribute to odors.

Check what you can safely see

Without opening energized equipment, look for obvious water around accessible equipment, drainage problems, dirty accessible filters, and nearby moisture.

Could the smell come from somewhere else?

Musty odors can also originate from wet building materials, plumbing leaks, basements or crawlspaces, and other moisture sources.

When should I get help?

Have the system evaluated when the smell persists, is getting stronger, is accompanied by visible moisture, or appears after a leak or water event. Find Local HVAC Help