A systematic evaluation of the operating parameters for four commercially available in-stack cascade impactors was carried out with polydisperse test aerosols. Test aerosols used were polystyrene latex spheres, uranine, sodium chloride, dioctyl-phthalate, or dinonyl phthalate. The effect upon the apparent measured size distribution of each polydisperse test aerosol was noted for various gas sampling rates (flow rates), types of impactor collection surfaces (glass fiber, uncoated aluminum, and aluminum coated with silicone), stage loadings and interstage losses. Collection surfaces were further characterized as to their weight loss during exposure to elevated temperatures and their tendency to be blown off by an impinging jet of air. Measurements revealed that interstage losses may amount to 30% of the total collected mass; however, there is little effect upon the apparent measured size distribution when these losses are ignored. The useful range of flow rates available for the impactors was defined at the lower end by a loss of useful sizing data and at the upper end by the presence of particle bounce off the latter stages. In general, the impactors were found to give similar apparent measured size distributions when operated at various flow rates within this useful range. Recommendations were made for: (1) optimum operation of the impactor when sampling various types of aerosols, and (2) accounting for observed or known errors in the data.

"EPA-600/2-80-048." "February 1980." Performing organization: Dept. of Environmental Engineering Sciences, University of Florida. Project officer: Kenneth T. Knapp, Emissions Measurement and Characterization Division, Environmental Sciences Research Laboratory. Includes bibliographical references (pages 107-109). U.S. Environmental Protection Agency.