2020 No https://doi.org/10.1016/j.envpol.2020.115107 Tong, Zheming Asia Experimental Exposure Study Students Elementary (K-5) Ventilation rates Carbon Dioxide (CO2) Particulate Matter (PM) Air filtration unit Ventilation Classrooms China PM 2.5 IAQ Field experiment compared air filtration unit impacts on PM₂.₅ exposure in Chinese primary school classrooms; findings guide ventilation strategies and public health decisions.