Ask Absolute · Air quality

Why does the air from my vents smell musty?

Direct answer

Musty odor can come from moisture, drainage, an indoor coil or cabinet, duct materials, filters or a building source drawn into the return air.

What this usually means

Replace a dirty filter and note whether odor appears only at startup or throughout operation. Do not assume duct cleaning alone will solve a moisture source.

An evaluation should trace where moisture and odor enter the air path and correct the source when possible.

What you can safely check

  • Filter condition
  • Visible water near equipment
  • Startup-only or continuous odor
  • Rooms where odor is strongest
When to call a professional

Call when odor persists, water is present, occupants experience irritation or visible growth is suspected.

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