Which of the following is an example of an EPA-approved FEM PM2.5 method?

• A. A continuous mass monitor validated as equivalent to the FRM.
• B. A gravimetric filter used after a rain event.
• C. An optical particle counter not validated.
• D. A handheld device for indoor air.

Answer: (A)

Federal Equivalent Methods are EPA-approved alternatives to the Federal Reference Method for PM2.5 that have been shown to produce results equivalent to the FRM. A continuous mass monitor that has been validated as equivalent to the FRM clearly meets that standard, because its performance has been demonstrated to match FRM under EPA criteria and thus it can be designated as an FEM for official ambient monitoring. The other options do not carry that EPA-approved FEM designation: a gravimetric filter is a FRM-type method, not necessarily an FEM unless EPA explicitly designates it as such; an optical particle counter that hasn’t been validated lacks the required EPA validation; and a handheld indoor device isn’t appropriate for ambient outdoor PM2.5 FEM use.