Quality Assurance Guidance - Monitoring PM2.5 in Ambient Air Using Designated Reference or Class I Equivalent Methods

This document is intended to provide additional guidance to assist personnel using reference methods or Class I equivalent methods to monitor ambient air for particles with an aerodynamic diameter nominally equal to or less than 2.5 micrometers (ȝm), known as PM2.5. The formal specifications for PM2.5 reference method samplers and reference method measurements are set forth in the U.S. Environmental Protection Agency’s (EPA’s) monitoring regulations – 40 Code of Federal Regulations (CFR) Part 50, Appendix L (EPA 1997a).* The regulations governing the sampling and analytical methods must be followed. This document reviews those formal requirements and provides clarifications and supplemental information in greater detail than can be provided in the formal regulatory requirements. Because this supplemental information is intended for method users, it emphasizes the operational aspects of the method, rather than the design and performance specifications for the sampler