A submicron aerosol generator has been described. The generator combines pneumatic atomization with electrostatic classification to produce uniform particles from 0.01 to 0.5 μm at concentrations up to 106 particles/cc. The particle diameter accuracy of the aerosols is about 2%, and the concentration accuracy about 5%. This submicron aerosol generator has been used to produce NaCl aerosols as absolute calibration standards for condensation nuclei counters. Calibration results are presented showing that the Environment/One (Model Rich 100) counter has a linear response at concentration levels up to 130,000 particles/cc, but the indicated concentration based on the accepted Nolan-Pollak standard is lower than the acutal concentration by a factor of 2.5. Above an aerosol concentration of 130,000 particles/cc, the instrument response becomes nonlinear, but the response is independent of particle size (0.011-0.15 μm in diameter) in both the linear and nonlinear ranges. Similar studies of the General Electric counter showed that the instrument response is linear to the highest concentration level (65,000) used in the studies. Results of these experimental findings are discussed, and their implications in coagulation-coefficient and particle-diffusion measurements are considered.
Bibliographical noteFunding Information:
This research was supported under Environmental Protection Agency Grant No. 801301; the Agency's support of this work is gratefully acknowledged. The authors thank Mr. T. A. Rich for his critical review of the manuscript and for his helpful comments. Dr. David Sinclair's suggestions are also gratefully acknowledged.