Abstract
Indoor air quality significantly affects occupants' health, making it crucial to evaluate a building's vulnerability to air pollution. In this study, 17 classrooms in urban areas of Seoul, Korea were monitored to determine how long a clean air environment can be maintained. We propose the balance point concentration (BPC) as the threshold value of outdoor PM2.5 concentration that can maintain PM2.5 in classrooms at the target value of 15 ÎŒg/m3. Based on the mass-balance equation, BPC is a comprehensive indicator that considers PM2.5 that can penetrate through building envelope, be generated from indoor activities, and be removed by an air purification system. For non-occupied classrooms, the BPC ranged from 20.6 to 34.3 ÎŒg/m3. We find that better airtightness reduced air pollution in buildings. However, due to students' activities, BPC decreased to 7.6â12.0 ÎŒg/m3. Lastly, in classrooms with mechanical ventilation systems in operation, the BPC ranged from 24.3 to 34.2 ÎŒg/m3, showing improved performance. Under such conditions, students can spend more than 88 % of the year in a classroom environment with clean air. In areas with low outdoor pollution levels, satisfaction can be even higher. Evaluating buildings performance using BPC allows for a more intuitive and clear assessment compared to existing indicators. When outdoor concentrations exceed BPC, additional air quality management in the classroom is necessary. This can be widely utilized when planning improvements to the environment or the operation of air purification system.
Published Version
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