The Ddevelopment and Designation Testing of a New USEPA-Approved Fine Particle Inlet: A Study of the USEPA Designation Process

This article discusses the practical challenge of meeting USEPA requirements for equivalency between novel particulate matter monitoring instruments and the USEPA WINS PM2.5 Impactor (i.e., the Federal Reference Method sampler for fine particulate matter). A project was undertaken to develop a new PM2.5 instrument in which the WINS impactor was substituted by a cyclone, to give superior performance over long sampling periods under heavy loading. Empirical cyclone models were used to develop a new generation of very sharp cut cyclones (VSCC), together with a particular VSCC specimen suited to PM2.5 sampling at 16.67 l min−1. In laboratory tests, this VSCC demonstrated a precise 2.5 μm D50 cutpoint and sharpness as good as the WINS. A formal application was then undertaken to achieve USEPA Class II Equivalency designation. The process included aerosol laboratory loading trials, with results showing no change in cutpoint after up to 90 days between cleaning cycles. Field trials to compare the VSCC to the WINS FRM were then performed in both western and eastern air sheds to demonstrate the precision and accuracy of the candidate VSCC FEM. The results showed that the VSCC instrument yielded precision and accuracy within USEPA requirements, although the USEPA data requirements for the field trials (in terms of aerosol size distribution and concentration) were not fully met. The outcome of the project was that the Class II equivalency designation was achieved, but not without major difficulties in gathering suitable and sufficient data to meet the stringent test requirements laid down by USEPA. Some changes in the designation procedure are recommended in light of this experience.