Research Projects

Project at a Glance

Project Status: complete

Title: Size-selective monitoring techniques for particulate matter in California air

Principal Investigator / Author(s): John, Walter

Contractor: Air and Industrial Hygiene Laboratory, California Department of Health Services

Contract Number: A5-00487

Research Program Area: Atmospheric Processes

Topic Areas: Monitoring


After a review of the criteria for a suitable size-selective monitoring instrument, the dichotomous virtual impactor and the cyclone were selected for evaluation. A cyclone was designed with a 50% cutoff of 3.5 m at 15 l/min. The cyclone and the Sierra Model 243 dichotomus virtual impactor were tested extensively with menodisperse aerosol including both solid and liquid particles. Detailed measurements were made of particle deposition in the samplers as a function of particle size and air flow rate. Wall losses, reentrainment and uniformity of filter deposits were determined. The results of the tests show that both samplers are satisfactory for monitoring purposes.

A preliminary investigation was made of the stacked filter unit. Measurements of the filtration efficiency of the 8 m pore size Nuclepore filter indicate that particle bounce is an important problem and that the particles are sized geometrically. Additional work is necessary to establish the characteristics of the stacked filter unit.

A manifold was designed for particulate sampling in ambient air. The inlet has a 50% cutoff of 20 m. A new impaction surface, oil-soaked sintered metal, eliminates particle bounce, even with heavy loading. The manifold is equipped with an eight-sector wind run acquisition system.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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