Assessment of PM2.5 penetration based on airflow paths in Korean classrooms

PM2.5 in classrooms adversely affect the health of young children, underscoring the importance of maintaining indoor air quality. In many Korean schools, the airtightness between a corridor and classrooms is not adequately tight. This lack of airtightness implies that corridors, often having high PM2.5 concentrations, significantly contribute to the degradation of classroom air quality. While some studies have acknowledged corridors as a key source of PM2.5 infiltration, few have quantitatively assessed the amount and frequency of PM2.5 entering classrooms through these pathways. This study examined the pattern and quantity of PM2.5 penetrating from the outdoor and corridor into classrooms in a typical Korean school. In south-facing classrooms, much of the infiltrating air originated directly from external walls, with a minimal amount coming from the corridor. However, given the corridor's relatively high PM2.5 concentration and significant penetration, approximately 25% of the total PM2.5 infiltration was attributed to the corridor. In contrast, east- and west-facing classrooms, influenced by Korea's prevalent westerly winds, experienced a pronounced increase in air entering the room, particularly from the corridor. Although the PM2.5 concentration in the corridor was lower than that in the south-facing classroom, the heightened airflow indicated that the corridor was responsible for 79% and 58% of PM2.5 infiltration in eastand west-facing classrooms, respectively. The results indicate that corridors' contribution to classroom PM2.5 levels is substantial; therefore, enhancing the airtightness between corridor and outdoor is crucial to reducing corridor PM2.5 levels. Alternatively, improving the airtightness between classrooms and corridor can effectively mitigate PM2.5 penetration.