Interactions between indoor and outdoor particulate matter in different microenvironments on a university campus

Indoor air quality (IAQ) has significant impacts on human health. High variabilities in indoor pollution levels are often expected due to co-impacts of complex outdoor and indoor sources and air exchange conditions. By using low-cost sensors, this study aimed to examine the differences in air pollutant concentrations between different indoor and outdoor environments including a dormitory, an office, a laboratory, a classroom, a dining hall and a library in a university campus. Generally, indoor particulate matter (PM) concentrations were lower than outdoor levels, with an overall indoor/outdoor (I/O) ratio predominantly <1. Indoor human activities (e.g. breathing, exercise, the use of air conditioning or electronic equipment), along with environmental factors such as temperature and relative humidity, co-affected the variation of indoor PM significantly. The results showed that the low PM concentration and exposure of students in the dinning hall could benefit from its good ventilation and frequent cleaning measures. Indoor air pollution from outdoor air pollution sources in the office contributed more to IAQ than in other locations. Enhanced ventilation and regular cleaning emerged as effective strategies for improving IAQ. These findings held important implications for comprehending the indoor–outdoor dynamics of diverse building air pollutants on campuses and their potential impacts on its population, offering valuable insights for enhancing IAQ.