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.