A Handheld Electrostatic Precipitator for Sampling Airborne Particles and Nanoparticles

Abstract

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.

Raman spectroscopy and TEM characterization of solid particulate matter emitted from soot generators and aircraft turbine engines

“…particle samples. In this device, a high-voltage electric field (»5 kV), created using a sharp needle as the anode and a flat surface as the cathode, charges the particles during the corona discharge (Miller et al 2010). The electric field drives the particles toward a grounded platform onto which the sampling substrate has been attached.…”

Development of a Transfer Function for a Personal, Thermophoretic Nanoparticle Sampler

“…Electrostatic precipitators (ESPs) have also been employed to collect airborne nanoparticles (Miller et al 2010). The advantages of ESP technology include high collection efficiency, low pressure drop, and a flat collection substrate.…”

“…However, ESP technology also has drawbacks. First, collection efficiency varies with particle size (Cardello et al 2002;Miller et al 2010) and tends to drop off precipitously below 20 nm (Cardello et al 2002). Second, the corona discharge creates reactive ions such as O + 2 and H 3 O + (Dzidic et al 1976) that charge the aerosol, but also creates oxidizing agents such as O 3 and NO x (Nashimoto 1988) that can alter particles' surface chemistry and cause a chemical artifact on the sample (Kaupp and Umlauf 1992;Volckens and Leith 2002a,b).…”

Aerosol sampling using an electrostatic precipitator integrated with a microfluidic interface

“…in air purifiers, but only recently have they been considered as a potential method for the capture of exhaled bioaerosols. Miller et al [38] demonstrated a hand-held ESP device for breath sampling relying on transmission electron microscopy (TEM) for sample analysis, which is not a suitable detection method for PoC applications. Alternatively, Kettleson et al [39] demonstrated inactivation of aerosolized viruses using an ESP.…”