10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Evaluating Performance of Low-Cost Optical Particle Counters in Sensing Bioaerosols; an Experimental Chamber Study
PARICHEHR SALIMIFARD, Donghyun Rim, James Freihaut, The Pennsylvania State University
Abstract Number: 1184 Working Group: Low-Cost and Portable Sensors
Abstract Recent rise of low-cost aerosol sensing technology has opened a new horizon in the study of particulate matter (PM) exposure with a broad range of applications; from establishing outdoor PM monitoring networks with high spatiotemporal resolutions; to integrating indoor PM sensors into building ventilation controls to mitigate PM exposure in occupied spaces. In order to reliably use low-cost sensors for any of the aforementioned applications, their performance under any of specific application conditions should be fully examined first. Various studies have conducted field and lab experiments to investigate the low-cost optical particle counters’ (OPC) performance. The results showed a strong dependence of the tested low-cost OPCs on the particle characteristics and environment conditions. Although, it is evident that low-cost PM sensor performances could vary considerably when exposed to various particles, very little information about the performance of low-cost sensors in monitoring bioaerosols is available. Given the significance of bioaerosols in exposure studies and their associated adverse health effects, this study investigates the performance of low-cost optical sensors in detecting the common indoor bioaerosols.
To investigate the effects of particle characteristics and concentrations, PM sensor responses were examined under exposure to varying concentration levels of biological (dust mite, pollen, cat fur, and dog fur) and non-biological (monodisperse silica and melamine resin particles in 1 and 2.8 µm) aerosols. Each particle sample was dispersed into a chamber (76×76×42 cm) using a computer-controlled syringe injection system. Size-resolved particle number concentration was measured by four tested low-cost OPCs (Speck, Airviz Inc.; Dylos, Dylos; OPC N2, Alphasense; and IC Sentinel, Oberon Inc.) and the reference sensor (AeroTrak, TSI) simultaneously. Linear regression analysis was used to compare the sensor responses to that of the reference sensor.
Results showed different combined effects of aerosol size, optical characteristics, and concentration on the sensor response. Concentration has the most dominant effect on the linearity of the low-cost sensors. In lower particle number concentration ranges, low-cost PM sensors showed nonlinear response, whereas, in higher concentration ranges they exhibited high linearity. The dividing line between the nonlinear and linear concentration regions varied with the sensor and the tested non-biological aerosol type and size. The fairly homogenous response to the bioaerosols allowed for determining a dividing line (5/cm3) between nonlinear and linear regions that is common amongst all the tested low-cost OPCs. This study findings imply that low-cost OPCs can be used in monitoring specific concentration ranges of bioaerosols, once they are calibrated prior to deployment.