The report summarizes the investigations of four aerosol classifiers which cover finite, but overlapping ranges of the aerosol particle size spectrum. The first part is concerned with a cylindrical aerosol centrifuge, which measures aerodynamic equivalent diameters precisely. This instrument has been used as a reference instrument in diffusion battery experiments reported in the second part. The diffusion battery has been investigated for fairly large particle sizes (0.3 micrometer to 0.5 micrometer) to determine the influence of sedimentation, interception and impaction on the transmission of the diffusion battery. These experiments have been performed with highly monodispersed NaCl aerosols. In the third part a five stage low pressure impactor is described, which covers the size range from 0.1 micrometer to 25 micrometers diameter. It has been developed specifically for the determination of the deposited particulate mass. First data on mass-size distributions of atmospheric aerosols are reported. The final chapter summarizes the development of a special condensation nuclei counter which measures number-size distributions in the size range from 0.002 micrometers to 0.1 micrometers KELVIN-equivalent diameter. The applicability to urban atmospheric aerosols is demonstrated.

"EPA-600/2-79-105." EPA research grant no. 801983; EPA project officer: Jack Wagman. Includes bibliographical references (pages 87-91).