2021 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10230515/ Lee, Bong Gu Asia Observational Modeling Elementary (K-5) Bacteria Fungi Classroom air Elementary school classrooms Microbial communities Next generation sequencing The bacterial community was richer in outdoor air than classroom air, whereas fungal diversity was similar indoors and outdoors. Bacteria such as Enhydrobacter, Micrococcus, and Staphylococcus that are generally found in human skin, mucous membrane, and intestine were found in great abundance. For fungi, Cladosporium, Clitocybe, and Daedaleopsis were the most abundant genera in classroom air and mostly related to outdoor plants. Bacterial community composition in classroom air was similar among all classrooms but differed from that in outdoor air. However, indoor and outdoor fungal community compositions were similar for the same school but different among schools.