Federal reference and equivalent methods for measuring fine particulate matter

Abstract

In the national ambient air quality standards specified by the U.S. Environmental Protection Agency in the Code of Federal Regulations, new standards were established for particulate matter on July 18, 1997. The new particulate matter standards specify mass concentration as the indicator for tine particulate matter (aerodynamic diameter of 2.5 μm or less). Ambient measurements for the new particulate standard must be performed by a new federal reference method as specified in the Code of Federal Regulations or by an alternative measurement method that has been designated by the Environmental Protection Agency as an equivalent method. The new particulate reference method is a 24 h integrated sample collected from the ambient air and analyzed gravimetrically. The reference method is explicitly specified using a combination of design- and performance-based criteria. Additional requirements listed in the Code of Federal Regulations address conditioning, handling, and weighing of the sample filter, which are performed manually. For alternative measurement techniques that do not meet the qualifications of the reference method, the Environmental Protection Agency defines three classes of candidate PM2.5 equivalent methods based on the measurement technique used and its degree of similarity to the reference method specifications.