Coincidence effect of a low-cost particulate matter sensor: Observations from environmental chamber tests at diverse particle concentrations

Particulate matter (PM) poses significant environmental and public health concerns, particularly in urban areas, where elevated PM levels are associated with increased risks of respiratory and cardiovascular diseases. This study assesses the performance of the PMS7003, a low-cost portable PM sensor (LCS) based on light-scattering technology, under controlled environmental chamber conditions. The PMS7003 measures PM concentrations by detecting the intensity of light scattered by particles passing through a detection zone. Our findings reveal that the LCS provides relatively accurate measurements of PM_1.0, with an underestimation of only 4%. However, it significantly overestimates larger particles, with an overestimation of 72% for PM_2.5 and 92% for PM₁₀. This discrepancy is attributed to the coincidence effect, where multiple smaller particles are misidentified as larger ones when they pass through the detection zone simultaneously. Additionally, the LCS exhibits a saturation limit at high PM concentrations, leading to deviations from reference sensor readings. While prior research has largely focused on environmental factors such as humidity and temperature, this study specifically investigates the impact of the coincidence effect on sensor performance. The results highlight both the advantages and limitations of LCS, emphasizing the need for advanced calibration methods to improve data reliability for public health and environmental monitoring.