iaq
Mold in Air Ducts: How to Spot It, When to Worry, What We Can (and Can't) Do
Honest scope: what duct cleaning covers vs. what needs a mold remediation contractor.
By Yaniv Asayag · April 20, 2026
Maryland summers are humid. Inside air ducts, that humidity meets dust, which means: mold has the conditions it needs. If you smell musty air every time the AC kicks on, it's worth having the system inspected — moisture and microbial growth somewhere in the system are a common cause.
What to look for (visible signs)
- Black or dark green growth on supply register grills
- Musty smell within the first 60 seconds of AC startup
- Condensation pooling in the supply trunk near the air handler
What an Eagle cleaning can fix
Surface mold on duct interiors, biofilm in the air handler, dust + mold mixture in the trunk — yes. We HEPA-vacuum it out, brush the duct walls, and apply EPA-registered antimicrobial fog. The post-cleaning IAQ Lab Report shows the mold spore count before and after.
What requires a mold remediation contractor
If mold has grown into drywall, behind a vapor barrier, inside the home's structure (not just the ducts), or if the affected area exceeds 10 square feet — that's remediation work and we will refer you. Mold remediation is a separate trade from duct cleaning; we don't do it and won't pretend to.
Aeroseal sealing if it keeps coming back
Some homes have leaky supply ducts pulling humid attic air across cooled surfaces. The condensation feeds repeat mold. Aeroseal duct sealing (a separate service we don't offer but can refer for) closes those leaks at the source.
Ready for a free written quote?
Every Maryland home is different. Tell us about yours — we come look and quote in writing.