“…The complex indoor environment contains many factors that affect indoor microbial concentration, including particles of different particle sizes, carbon dioxide (CO 2 ), temperature, humidity, ventilation rate, season, height, etc. [4][5][6][7][8][9][10][11][12][13] Epidemiological evidence shows that there is a relationship between indoor pollutants and health risks, 14 and indoor pollutants of concern include particulate matter (PM), biological organisms (fungal spores, bacteria, and viruses), allergens, over 400 different chemical compounds, mainly volatile organic compounds (VOCs) such as benzene, toluene, methanol, ethylbenzene and xylene, inorganic compounds (ICs) such as carbon monoxide (CO), carbon dioxide (CO 2 ), nitrogen oxides (NO x ) and ozone (O 3 ), among others. 15,16 Given that 5%-34% of particulate matter (PM) in indoor air is in the form of bioaerosols (i.e., bacteria), 17 these bioaerosols are accompanied by many harmful microorganisms and viruses, such as SARS-CoV-2 and other viruses, which are spread through bioaerosols.…”