A Handheld Electrostatic Precipitator for Sampling Airborne Particles and Nanoparticles

Researchers at NIOSH are developing methods for characterizing ultrafine aerosols in workplaces. One method includes the detailed analysis of collected particles using electron microscopy (EM). In order to collect samples for EM at remote workplaces including mining and manufacturing facilities, researchers have developed a handheld electrostatic precipitator (ESP) particle sampler capable of collecting airborne particles including nanoscale materials, for subsequent EM analysis. The handheld ESP has been tested in the laboratory and is currently undergoing beta testing in the field. Gross collection efficiencies were measured with a CPC and net efficiencies by EM analysis of collected samples. Using laboratory-generated NaCl aerosols in the 30-400 nm size range at a flow rate of 55 cc/min and ESP operating voltages between 5.6-6.8 kV, both gross and net efficiencies were measured and showed a similar correlation with voltage, with maximum efficiency of approximately 86% at 6.4 kV. EM images from samples were also used to estimate particle size distributions of the original aerosols and the size-dependent deposition was evaluated for upstream versus downstream locations on the sample media. Results suggest that the number concentration and particle size distribution of sampled aerosols may potentially be estimated from a single ESP sample, but that the accuracy and repeatability of such quantification need to be investigated and refined. NIOSH is planning to license the ESP sampler for commercial manufacturing.