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Under the Asbestos Hazard Emergency Response Act (AHERA), when acquiring samples of multi-layered material such as wallboard, do you sample both the wallboard and the joint compound as separate materials or can you take a weighted average of both?

As stated in the January 5, 1994 Asbestos Sampling Bulletin clarification, joint compound and wallboard form a “wall system,” and the Environmental Protection Agency (EPA) therefore recommends the use of a composite analysis for this material. See 59 FR 542; see also 60 FR 65243 (1995). For joint compound (not skim coat), EPA recommends that an accredited inspector take a weighted average of the different wall system components to arrive at the final reportable number.