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What are they wanting to know?
Most just want the areas that have leaked tested. If any of the areas comes back considered toxic than perform more testing to determine how much of an area needs to be cleaned up. I would suggest a full visual inspection first before testing.
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The way I see it you can charge them whatever you want because in the end the sample results you obtain will likely not mean anything. That is to say, you will likely not be able to develop conclusive results. For several of the projects on which I worked at NIOSH, we tried with bunches more samples on all kinds of buildings. In the end, knowledge of the building dynamics and observations with a few airflow and particle counter measurements helped develop better conclusions than trying to fungally “characterize” a building.
I totally agree with James on this one. Good luck with that and laugh all the way to the bank.