A review of indoor air quality (IAQ) in classrooms: The effect of particulate matter (PM), gaseous pollutants, and airborne pathogens.

Indoor air quality (IAQ) in classrooms raises major public health concerns, as evidence links pollutants with harmful effects. Global research reports pollutant levels exceeding guidelines due to high occupancy, weak ventilation, and outdoor infiltration. Particulate and gaseous pollutants trigger respiratory symptoms, aggravate asthma, reduce comfort, and impair students' cognitive abilities. Rising CO2 levels and insufficient ventilation signal heightened risks of airborne infection in occupied classrooms. Mechanical ventilation and filtration technologies reduce pollutant loads, though performance varies across school conditions. Unlike existing reviews, this study comprehensively integrates particulate matter, gaseous pollutants, carbon dioxide, and airborne pathogen transmission. It combines bibliometric mapping with multi-pollutant and ventilation-based analysis to reveal critical research and implementation gaps. The findings also provide an interdisciplinary framework supporting evidence-based classroom design, ventilation optimization, and infection risk mitigation.