Characteristics of PM2.5 and CO2 Concentrations in Typical Functional Areas of a University Campus in Beijing Based on Low-Cost Sensor Monitoring

The air quality in educational campuses affects the health and work efficiency of teachers and students. Studies into this matter are of great significance for optimizing the management of campus living environments. Low-cost online sensors to monitor PM2.5 and CO2 levels were used in typical functional areas of a university campus in Beijing, China, including offices, dormitories, leisure spaces, canteens, and laboratories. By comparing the findings with data from nearby national monitoring stations, the seasonal and spatial variations in PM2.5 and CO2 concentrations were analyzed. Findings indicate PM2.5 levels within the campus were notably lower compared to the surrounding urban environment. There was variation in PM2.5 and CO2 concentrations across different functional areas. Typically, indoor PM2.5 levels were lower than outdoor ones, while CO2 concentrations in enclosed indoor spaces with human activities progressively escalated. The main internal emission sources affecting the PM2.5 level on campus included traffic emissions, dust generated by human activities, and emissions from catering. In contrast, in areas with better green coverage or where a lake system participates in the atmospheric circulation, the PM2.5 level and CO2/PM2.5 were lower. This indicates that the cleansing impact of plants and aquatic systems is instrumental in lowering PM2.5 concentrations, offering healthier leisure spaces. Seasonal variations also impact PM2.5 levels. During the non-heating period, less pollution source emissions led to decreased outdoor PM2.5 concentrations. The campus monitoring sites experienced an approximate 5 µg/m3 and 29 µg/m3 reduction in the average PM2.5 levels as compared to the PM2.5 of the surrounding urban environment, respectively, during the non-heating and heating period. During indoor activities or sleep, CO2 levels can build up to as high as 2303 ppm due to breathing. It is advisable to stay indoors on days when pollution levels are high, whereas on days with clean air, it is healthier to be outdoors or to air out indoor areas by opening windows. Our research provides clearer scientific evidence for incorporating behavioral strategies for improving air quality into both daily work and life. Moreover, the findings are quite meaningful for the widespread adoption of low-cost sensor monitoring in various environments, with applications beyond just the campus settings.