Determining Ultrafine Particle Collection Efficiency in a Nanometer Aerosol Sampler

Abstract

The Nanometer Aerosol Sampler (NAS, Model 3089) manufactured by TSI Incorporated (Minnesota, USA) is commonly used to collect ultrafine particles (UFPs, diameter < 100 nm) for off-line analysis. However, the UFP collection efficiency for this instrument has only been reported for polystyrene latex (PSL) particles at a flow rate of 1 L· min–1 and a voltage of 10 KV. To expand the applicability of the NAS and determine the optimal conditions for collecting the greatest amount of UFPs for a given time, three types of UFPs (PSL, candle smoke particles, and diesel exhaust particles) were collected across a flow rate range of 1–4 L· min–1 and an applied voltage range of 1.0 to 9.3 KV. The experimental results indicate that at identical conditions, the PSL particle collection efficiency in the TSI instrument manual (43% to 8%) was lower than the measured efficiency of candle smoke particles (99.5% to 39%) and diesel exhaust particles (99% to 32%). Decreasing the flow rate and increasing the voltage increased the collection efficiency, with the highest efficiency obtained at 1 L· min–1 and 9.3 KV. However, the NAS collected the greatest amount of UFPs at 4 L· min–1 and 9.3 KV, since the voltage had more of an impact on UFP collection efficiency than did the flow rate. After modifying a well-established electrostatic precipitator (ESP) model by introducing a factor F, which is a function of the electric Peclet number and the flow rate, agreement with the experimental results was obtained.