Tenant Mold Complaint

[Tonna Lee]

I investigated, tested humidity and moisture and found no problem. Nothing wet, no stains any where.  I realize I might not be seeing it.  Had friend who was a retired plumber of 25 years and mold experience with me.  Other tenant is retired from 30-years at Housing Authority and said prior to my testing that there is no mold.   Wrote findings and recommendations and gave to tenant.

Am I required to hire a professional?  Should I go ahead and hire a professional?  Should I charge tenant for cost of professional?  I live in the other half of the duplex.  Thank you