Assessing the impact of air purifier and scheduled natural ventilation on pollution-ventilation nexus in a near highway infant school

Abstract

The combined application of technological intervention and natural ventilation were studied by using air purifier and window opening to investigate their effect on classroom air quality (CAQ) in two classrooms of an infant school. One classroom was located adjacent to the highway (classroom A) and occupied by younger students, and the other was away from the highway and occupied by older students (classroom B). Four ventilation scenarios along with the use of HEPA air purifier were studied; (1) partial ventilation (single window open); (2) continuous ventilation (all windows open); (3) no ventilation (all windows closed) and air purifier in operation and (4) scheduled ventilation (windows opened during non-occupancy period) and using air purifier during occupancy period. Partial ventilation has up to 27%, 18% and 9% improvement in PM10, PM2.5 and CO2 concentration respectively in classroom B, with no improvement in classroom A. Continuous ventilation resulted in 15%, 6% and 21% reduction in PM10, PM2.5 and CO2 concentration, respectively, in classroom A and no improvement in classroom B. Using air purifier with windows closed has no effect on CAQ in classroom A and 18%, 17% reduction in PM10 and PM2.5 concentration, respectively, in classroom B. Scheduled ventilation using air purifier resulted in reduction of up to 36%, 14% and 28% in PM10, PM2.5 and CO2 concentration, respectively, depending upon the classroom. No change found in PM1 concentration in both the classrooms under all ventilation scenarios. The CAQ and the effectiveness of the interventions depend on children's activities, classroom layout and teachers’ ventilation behaviour which is affected by classroom's proximity to highway. The CAQ and thermal comfort can be improved significantly in a more cost-efficient way by strategizing the application of technological and natural interventions in a naturally ventilated classroom.