Abstract View
Laboratory Calibration of a Low-cost Particulate Matter Sensor Using Standardized Aerosols
CHING-HSUAN HUANG, Jiayang He, Elena Austin, Edmund Seto, Igor Novosselov, University of Washington
Abstract Number: 421
Working Group: Instrumentation and Methods
Abstract
Particle deposition in human respiratory tract and the resultant adverse health effects depend on particles' size distribution, making direct measurement of time- and size-resolved particulate matter (PM) concentrations essential to health-related research. Some commercially available low-cost PM sensors provide output as total or size-specific particle counts and mass concentrations. These quantities are not measured directly but are estimated by the original equipment manufacturers' (OEM) proprietary algorithms and have inherent limitations because particle scattering depends on the particles' composition, size, shape, and complex index of refraction (CRI). Furthermore, environmental conditions such as relative humidity can also affect particle light scattering measurements. Hence, there is a need to characterize and calibrate their performance under a controlled environment and standardized test aerosols. Here, we developed calibration algorithms for a low-cost PM sensor as a function of particle size and mass concentration. A standardized laboratory experimental protocol was developed to control the PM concentration, environmental conditions, and sensor-to-sensor reproducibility. The calibration was based on tests when sensors were exposed to different polydisperse standardized testing aerosols. The results suggested linear model without adjusting aerosol properties, including CRI, density, and relative humidity was able to correct the raw, uncalibrated low-cost PM sensor number concentration measurements with normalized mean absolute error within 4.0% compared with the reference instrument. The calibration algorithms developed were most accurate for correcting PM < 2.5 µm (error < 2.9%). Linear models additionally adjusting for particle CRI and density demonstrated slightly lower error for calibration and may be used in scenarios such as industrial environments where specific known aerosols occur, but may be less useful for ambient environmental conditions where the aerosol composition is varied.