I tell them that I found mold. I know that a lot of inspectors are afraid of the "M" word, but you, I and they know that that is what it is. Mold needs t things to grow: moisture and organic material. Moisture is provided by the cold a/c causing condensation inside the duct. Organic material is in the form of dander and skin cells.
1. Duct cleaning may be in needed.
2. A de-humidifier may be needed.
3. Ducts in the crawl and/or attic may be disconnected allowing excess humidity in the home.
4. Bathrooms should be exhausted to the exterior with exhaust fans.
5. Crawl space (if present) moisture barrier and ventilation my need improvement.

Disclaimer:
Mold identification and testing is beyond the scope of a home inspection. I recommend that you contact an indoor air quality company for testing and remediation, if needed.

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Integrity Inspection Service, LLC
www.irsindy.com
(317) 345-1828