Perspec, Personal Size Separating Sampler: Operational Experience and Comparison with other Field Devices

Abstract

The basic information needed for a realistic evaluation of the inhalation risk to workers and the general population from particulates is the airborne mass concentration distribution over size. Proposed international standards define the inhalable (formerly called inspirable) fraction, those particles capable of entering the nose or mouth; the thoracic fraction, those capable of entering the lungs (d_a < about 10 μm); and the respirable fraction, those capable of entering the gas-exchange region of the lungs (d_a < about 3.5 μm). In addition, the extrathoracic fraction is defined as the difference between the inhalable and thoracic fractions, and the tracheobronchial fraction is defined as the difference between the thoracic and respirable fractions. The sampling efficiency of actual devices is expected to match that specified for ideal samplers within some tolerance, e.g., ±10 percent in the 50 percent cutpoint diameter and ±0.1 in the sharpness of the cut specified by a geometric standard deviation of 1.5 for the thoracic and respirable fractions.

These recommendations were used as specifications in the design of a personal sampler, PERSPEC (PERsonal SPECtrometer), which separated particles according to aerodynamic size and collected them on a circular 47- or 50-mm membrane filter with a sampling flow rate of 2 L/min. Because of the specific dynamic conditions inside the PERSPEC, larger particles reach the filter close to the center, while smaller ones deposit at the periphery. By two mechanical cuts, the filter can be separated into three parts, each containing a definite size range, i.e., respirable, tracheobronchial, and extrathoracic subfractions. Gravimetric assessment and chemical, physical, and biological analyses on each subfraction are possible. A cutting tool for a sharp and reproducible separation of the subfractions was built. Extensive comparisons were performed with existing samplers, specifically for “total” concentration and the respirable fraction. The results of these comparisons are presented together with monitoring data from several industrial operations.