Results of a comparative study between monitoring stations and real-time low-cost sensor measurements (PurpleAir) for PM2.5

Abstract

Background: Particulate matter in ambient air is an important risk factor for cardiovascular and respiratory diseases. Accurate and appropriate air quality monitoring is therefore critical for public health. In this context, it is necessary to investigate the feasibility of using low-cost direct monitoring devices (such as PurpleAir) in outdoor environments during the winter season, particularly in urban areas where fixed monitoring stations are not available. Aim: To assess and compare the outdoor PM2.5 concentrations in Ulaanbaatar and Darkhan during the winter season. Materials and Methods: The study was conducted in the capital city of Mongolia. The data collected for 45 days during the winter season, from December 9, 2024 to February 14, 2025. Continuous low-cost sensor was collected using a light scattering device (PurpleAir Classic) at a total of 25 locations and for 24 hours. Of these, 1 location was located next to a fixed measurement point and 3 locations (Zuun 4 zam, Yarmag, Selbe) were located within 200m of the study area, and the measurement results were compared using PM2.5. We used R software for statistical analysis. Results: The average PM2.5 concentration measured at the 13 fixed monitoring sites during the study period was 65 μg/ m³, while the average from the 25 PurpleAir sensors was 88 μg/m³. Parallel measurements conducted with the PurpleAir sensors and the UB4 fixed monitoring station showed a moderate correlation (r=0.44, R²=0.22, p<0.05). The measurement results at the Zuun 4 zam, Yarmag, and Selbe locations have a moderate correlation (r=0.38, r=0.61, r=0.25). Conclusion: In situations where it is not possible to measure PM2.5 particulate matter in outdoor air automatically or by conventional methods, it is possible to monitor air quality by measured by low-cost sensors.