Effect of clean air core geometry on fine particle contamination and calibration of a virtual impactor

Abstract

The optimum diameter and position of the clean air core in a clean air core virtual impactor were experimentally determined. It was found that the clean air core diameter should be at least twice as large as the converging nozzle diameter and that the clean air core should be positioned so that the ratio of the clean air flow velocity to the aerosol flow velocity ranges from 1.5 to 5.0 at the outlet of the clean air tube. Use of a laminator in a virtual impactor was found to increase the particle loss while maintaining almost the same collection efficiency curve. © 1997 American Association for Aerosol Research.