Indoor air quality (IAQ) in schools significantly affects health and academic performance; however, effective interventions for poor air quality remain limited, particularly in settings with restricted natural ventilation. This study evaluated the effectiveness of ventilation-type air purifiers in improving classroom IAQ in a South Korean elementary school. PM10, PM2.5, and CO2 concentrations were monitored over 18 days (14–31 May 2021) in two classrooms—one equipped with a ventilation-type air purifier and the other serving as a control. In the classroom with the air purifier, daily average concentrations of PM10, PM2.5, and CO2 decreased by 23.7%, 22.8%, and 21.1%, respectively, from baseline levels. The air purifier effectively reduced pollutant infiltration during periods of severe outdoor air pollution and stabilized pollutant levels during active class hours. Its efficacy was particularly prominent under conditions of restricted natural ventilation, high indoor activity, and fluctuating outdoor pollution levels. IAQ varied significantly between weekdays and weekends; pollutant levels were higher on weekdays due to occupancy and classroom activities, whereas weekends exhibited reduced concentrations. These findings suggest that ventilation-type air purifiers provide a viable strategy for improving IAQ in schools with limited ventilation. Future research should examine their long-term performance across different seasons and architectural settings.
