School air quality and thermal comfort: A multi-pollutant seasonal assessment

Abstract

As evidence of children’s vulnerability to air pollution grows, research on school air quality has increased significantly in the 21 st century. Given the complex factors influencing indoor and outdoor air quality in schools, each study offers valuable insights. This study contributes by assessing particulate matter, gaseous pollutants, thermal comfort and microorganisms in a large school encompassing different education levels over two seasons. The assessment combined passive and continuous sampling using various techniques, including chromatography and estimations of air change and ventilation rates. Classroom ventilation was insufficient to ensure adequate air renewal. During class hours, CO 2 concentrations ranged from 760 to 1,118 ppm in winter and from 807 to 1,022 ppm in spring, repeatedly exceeding 1,000 ppm. CO 2 and PM 10 concentrations were significantly higher during school hours than when the classrooms were empty, indicating the strong influence of school activities. In contrast, PM 1 and PM 2.5 concentrations were more influenced by external factors, especially outside of school hours. The lack of thermal comfort created an unhealthy environment. Carbonyl concentrations were higher in classrooms (average: 68.8 μg m -3 ) compared to the schoolyard (3.86 μg m -3 ), in both seasons. Microbial analysis revealed the presence of fungi with toxigenic potential, with the highest fungal diversity observed in spring. These findings highlight that while some pollutant levels may appear low, they can occasionally reach extremely high levels, even in newer buildings. The novelty of this research lies in demonstrating that, despite recent improvements and numerous studies, significant progress is still needed to ensure healthier school settings. • All classrooms showed poor thermal comfort conditions in winter. • Hourly average CO 2 frequently exceeded 1,000 ppm in both winter and spring. • Higher concentrations of formaldehyde and acetone were found indoors than outdoors. • Bacterial counts were highest in winter, while fungal counts peaked in spring.