The Effect of Air Purifiers in Schools

Francesco Granella (RFF- CMCC)

We randomize the installation of air purifiers across primary school classrooms to reduce children’s exposure to air pollution. The intervention reduces indoor PM2.5 concentrations by 32% and decreases student absenteeism by 12.5%. We find larger effects among students with higher pre-treatment absenteeism. The impact is also greater when outdoor air pollution is relatively low and diminishes as outdoor pollution intensifies, consistent with non-linear marginal effects of air quality on health. Treated students report fewer respiratory symptoms and exhibit greater awareness of air quality. Each avoided absence day costs approximately €11, yielding a conservative cost-benefit ratio of one-to-nine.