How often should air ducts be cleaned?

Duct cleaning earns its value cleaning up an actual accumulated problem — construction dust from a renovation, evidence of rodents or pests, visible mold after a water issue, or years of buildup in a home that's never had it done. For a typical home with a decent filter changed regularly, ducts don't need annual attention.

The honest tell that it's time: dust visibly blowing out of registers when the system kicks on, a musty smell when the AC or furnace runs, or recent construction work that would've sent debris into the system. Absent those signs, every 3–5 years is a reasonable interval, not a strict rule.