Abstract
ABSTRACT Electrostatic sampling is a promising method for the collection of bioaerosol particles. Although the underlying physics responsible for particle collection are well understood, the collection efficiency of simple passive electrostatic samplers is difficult to predict. Under these conditions, the collection efficiency becomes very sensitive to ambient air current and particle size, especially for submicron particles relevant for airborne virus transmission. In this paper, we compare two electrostatic aerosol sampler designs, a commercial product consisting of a flat collector plate located in the same plane as the charging needles and an axisymmetric design sampling directly to a liquid droplet. The aerosol particle collection efficiency of the samplers is investigated for particle size ranging from 0.25 to 2 µm while the air flow velocity surrounding the samplers is varied from 0.3 to 1 m s–1. For the planar design, at all ambient flow velocities, the submicron fraction of the particles captured originates in streamlines up to a maximum of 75 mm above the surface of the device collector, which greatly limits the volume of air being effectively sampled. The axisymmetric design features a non-monotonic capture efficiency as a function of particle size, with a minimum between 0.4 and 0.8 µm. The flow field in the inter-electrode region, captured using particle image velocimetry (PIV) reveals the presence of strong recirculation zones that can be responsible for the increased collection efficiency for very small particles.
Highlights
Bioaerosols are found nearly everywhere in both indoor and outdoor environments and they can affect the health of humans (Walser et al, 2015), animals (Van Leuken et al, 2016) and plants (Brown and Hovmøller, 2002)
The collection efficiency becomes very sensitive to ambient air current and particle size, especially for submicron particles relevant for airborne virus transmission
Two electrostatic samplers designed for the capture of bioaerosol particles are investigated to identify the effect of two key parameters on collection efficiency: the size of the particles and the velocity of air currents surrounding the samplers
Summary
Bioaerosols are found nearly everywhere in both indoor and outdoor environments and they can affect the health of humans (Walser et al, 2015), animals (Van Leuken et al, 2016) and plants (Brown and Hovmøller, 2002). Electrostatic precipitation (ESP), a technique already well-known for cleaning industrial gas streams, has been investigated for sampling airborne pathogens (Gerone et al, 1966; Kulkarni et al, 2011). This method brings interesting features, such as low mechanical stress on the particles collected, i.e. the deposition velocity is much lower compared to approaches based on inertial impaction (Willeke et al, 1995), meaning that mechanical stress is less likely to affect the infectivity of the pathogens
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