Effects of Optical Configuration on the Accuracy and Response of Low-Cost Optical Particle Counters

Hazards associated with air pollution motivate the search for technologies capable of monitoring individual exposure to gaseous pollutants and particle matter (PM). A Low-cost Optical Particle Counter (OPC), costing less than 50 USD, is an example of such technologies. Currently, OPCs are widely used to measure the concentration of PM in ambient air. While these low-cost air quality sensors are widely available, the accuracy and precision of these devices is highly uncertain. Consequently, the purpose of this paper is to present an analytical model of a generic, low-cost OPC based on Mie scattering theory. This model provides estimates of the minimum theoretical accuracy of commercially available, low-cost OPCs but does not address additional inaccuracy due to uncertainties in particle density, volumetric flow rate, and measured time. Modeling results indicate that measurement of forward-scattered light increases the accuracy of low-cost OPCs, and is concluded that the accuracy of these sensors may be significantly improved by optimizing the location of the photodetector.