The effect of air purifiers in improving classroom air quality in a primary school in Rwanda, East-Central Africa

Air pollution poses a severe public health challenge in Africa, where ambient particulate matter (PM) concentrations often far exceed World Health Organization (WHO) guidelines. Children are particularly vulnerable, spending long hours in poorly ventilated classrooms, which are often poorly constructed and designed, and inadequately maintained, and where indoor air quality (IAQ) is rarely monitored or improved. This study provides one of the first experimental evaluations of air purifiers (APs) in an African school environment in Rwanda. Minute-level measurements of PM 1 , PM 2.5 , and PM 10 were collected under two conditions (with and without AP operation) and classified into learning hours (LH) and non-learning hours (non-LH). Wilcoxon rank-sum tests and rank-biserial correlations were used to assess the effects of APs. AP use significantly lowered mean PM concentrations throughout the day (5.16% for PM 1 , 12.27% for PM 2.5 , 11.58% for PM 10 ). The amplification of the diurnal PM decline by APs during learning hours led to substantial reductions (29.79% for PM 1 , 33.12% for PM 2.5 , and 34.31% for PM 10 ), with significantly larger effect sizes compared to the no-AP condition. APs also accelerated PM 2.5 and PM 10 declines to below WHO Interim Target-1 (IT-1) thresholds (35 μg/m 3 and 70 μg/m 3 ) within 1.96 and 1.26 hours, respectively. These findings provide robust evidence that APs can rapidly and effectively improve IAQ in African schools, offering a feasible intervention to safeguard schoolchildren’s health and support healthier learning environments.