US EPA

1335802 

Journal Article 

Virtual Impactor as an Accessory to Optical Particle Counters 

Keskinen, J; Janka, K 

1987 

Yes 

Aerosol Science and Technology
ISSN: 0278-6826
EISSN: 1521-7388 

NIOSH/00167757 

6 

1 

79-83 

WOS:A1987G146900008 

A method for improving the sensitivity of optical particle counters for large particles was described. The method consisted of connecting the collection probe of a virtual impactor to the sample inlet of an optical particle counter. The increase in number concentration measured by the combination depended on the ratio of the measured concentration to the ambient concentration (No). The value of N/No depended on the large particle collection efficiency of the virtual impactor and obtained a maximum value (Kmax) that depended on the minor (sample) airflow and major airflow in the impactor. The combined system was calibrated with monodisperse 0.5 to 6 micron dioctyl-phthalate (DOP) particles. The system was then tested using DOP, methylene-blue, and Arizona road dust aerosols. Calibration yielded a Kmax of 21 which agreed with the theoretical value. The test aerosols showed that for particles having optical diameters larger than 3 microns, the number particle concentration was increased by a factor of 20. The authors conclude that the sensitivity of optical particle counters can be increased for particles larger than 3 microns by using a virtual impactor. Kmax values can be used to calculate the ambient particle concentrations. 

DCN-154148; Analytical instruments; Air sampling; Air sampling equipment; Dust particles; Particle counters; Dust sampling; Aerosol sampling; Analytical methods; Equipment design; Aerosol particles