2020 No https://onlinelibrary.wiley.com/doi/10.1111/ina.12734 Guo, Kangqi Asia Observational Epidemiology Study Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Bacteria Fungi Air quality Bacteria China Fungi Indoor Systematic review Results show that the concentration of indoor bacteria varies from 72.5 to 7500 CFU/m3, with a median value of 1000 CFU/m3, and the concentration of fungi varies from 12 to 9730 CFU/m3, with a median value of 526CFU/m3. The concentration level of microbes varies in different climate zones, with higher bacterial concentrations in the severe cold zone, and higher fungal concentrations in the hot summer and warm winter zone. Among different buildings, classrooms have the highest average bacteria and fungi levels.