Health Benefits of Air Purifiers in Primary School Students

The investigators will conduct a randomized controlled trial among 110 healthy children in Jiaozuo city, Henan, China. The eligible children will be divided into two groups according to their classes and randomly receive interventions of either true or sham air purifiers. The air purifiers devices in classroom \[air purifiers and fresh air ventilation systems\] will operate during the school time and the devices in bedrooms (air purifiers) operate during the home time in the intervention period. All the participants and investigators will be blinded to the group assignment. Epidemiological questionnaires (i.e., basic characteristics, eating habits, daily schedule, etc.) will be conducted and health indicators (i.e., blood pressure, pulmonary function indicators, fractional exhaled nitric oxide, and fractional exhaled carbon monoxide) and biological specimens (i.e., morning urine, venous blood, exhaled breath condensate, and feces) will be evaluated and collected at baseline and after the completion of intervention period (4 months anticipated).