Les I truly like your style and appreciate your position. I do let all clients know that I have other fields I work in hopefully not to get caught up in a conflict of interest. As to referring what appears to be a mold like substance (note the wording)in a home inspection if it is not mold? am I liable as a generalist? Or am I a expert in the mold field? That is why the labs decides. Even if I did not do mold analyst I still would not call it mold in my reports. Scott to answer your question no I am not a remediator or a expert in the mold remediation field. I generaly refer clients to www.epa.gov for general information. Or a professional remediator in that field. As to the return air box it was made of wood framing and sheetrock below the air handler it appeared a condensation issue was present and the rest was mold issues 101.