“…In Eq. (1) , denotes the EC of ATH sampling ( Kim et al, 2020a , Kim et al, 2020b ): where is the flow rate of the air, is the flow rate of the carrier liquid, and is the viral collection efficiency of the air sampler. Yang et al (2011) reported that there are relatively low concentrations of virus particles in indoor air (10 3 –10 4 viral genome copies per 1 m 3 of air) even during an influenza epidemic.…”