What is equivalency testing in PM2.5 monitoring?

• A. A process that compares a FRM method against a standard laboratory method to ensure regulatory use.
• B. A procedure to certify a monitor by repeated manufacturing checks.
• C. Demonstrating that a non-FRM method produces results that are equivalent to the FRM in accuracy and precision to be used for regulatory purposes.
• D. A training program for field technicians to calibrate instruments.

Answer: (C)

Equivalency testing in PM2.5 monitoring is the process of showing that a non-FRM method can produce results that are sufficiently close to the FRM in both accuracy and precision so that those results can be used for regulatory decisions. This involves co-locating the candidate monitor with an FRM monitor over a representative period and comparing the paired measurements. The analysis looks at how well the non-FRM values align with the FRM values—checking for bias, consistency (precision), and overall agreement using statistical criteria such as slope near 1, intercept near 0, good correlation, and acceptable differences within predefined limits. If the non-FRM method meets these criteria, its data are considered equivalent to the FRM for regulatory purposes; if not, the data from that method aren’t eligible for regulatory use until it demonstrates equivalence.