Evaluation of a novel personal nanoparticle sampler

Abstract

This work investigated the performance in terms of collection efficiency and aspiration efficiency of a personal sampler capable of collecting ultrafine particles (nanoparticles) in the occupational environment. This sampler consists of a cyclone for respirable particle classification, micro-orifice impactor stages with an acceleration nozzle to achieve nanoparticle classification and a backup filter to collect nanoparticles. Collection efficiencies of the cyclone and impactor stages were determined using monodisperse polystyrene latex and silver particles, respectively. Calibration of the cyclone and impactor stages showed 50% cut-off diameters of 3.95 mu m and 94.7 nm meeting the design requirements. Aspiration efficiencies of the sampler were tested in a wind tunnel with wind speeds of 0.5, 1.0, and 1.5 m s(-1). The test samplers were mounted on a full size mannequin with three orientations toward the wind direction (0 degrees, 90 degrees, and 180 degrees). Monodisperse oleic acid aerosols tagged with sodium fluorescein in the size range of 2 to 10 mu m were used in the test. For particles smaller than 2 mu m, the fluorescent polystyrene latex particles were generated by using nebulizers. For comparison of the aspiration efficiency, a NIOSH two-stage personal bioaerosol sampler was also tested. Results showed that the orientation-averaged aspiration efficiency for both samplers was close to the inhalable fraction curve. However, the direction of wind strongly affected the aspiration efficiency. The results also showed that the aspiration efficiency was not affected by the ratio of free-stream velocity to the velocity through the sampler orifice. Our evaluation showed that the current design of the personal sampler met the designed criteria for collecting nanoparticles <= 100 nm in occupational environments.