Abstract

Abstract. Poor air quality adversely affects children's respiratory health, yet few interventions have been reported to improve classroom indoor air quality (IAQ) in real school settings. Air purifiers can remove particulate matter (PM) and, by reducing airway inflammation, potentially enhance pulmonary function. This study aimed to evaluate the effectiveness of low-cost air purifiers on students' pulmonary function during winter. The study involved 97 students from 6th to 8th grades in Concepción, Chile. A pragmatic controlled trial was conducted using two types of air purifiers (A and B) that filter PM, with B being self-designed and built. Students served as their own controls. Indoor air quality was assessed over four weeks: the first week without intervention, followed by two weeks of alternating purifiers A and B, with washout periods of 2 to 7 days. Peak expiratory flow (PEF) was measured weekly, conducted by physiotherapists and trained students. A questionnaire was also administered to guardians to identify confounders such as health status and tobacco smoke exposure. Data were analyzed using generalized linear mixed models. Multivariable analysis revealed that air purifiers significantly improved students' PEF compared to the mean without intervention. For purifier A, the improvement was 3.1 percentage points (95% C.I. 0.6 to 5.9), and for purifier B, it was 4.0 percentage points (95% C.I. 1.8 to 6.1). In students with chronic respiratory conditions, purifier B enhanced PEF by 6.2 percentage points (95% C.I. 0.31 to 12.01), while purifier A showed a non-significant improvement of 5.23 percentage points (95% C.I. -0.62 to 11.07). The washout period (7 days or less) was non-significant and did not confound the purifiers' effect on PEF. Implementing air purifiers in classrooms effectively improves PEF and overall respiratory health among school-aged children, particularly those with chronic conditions. Continued research on classroom environmental conditions and their health impact is essential, as fewer respiratory illnesses lead to reduced absenteeism.