Experimental Understanding of the Flow Dynamics of Exhaled Air to Prevent Infection through Aerosol

Since several mass infections of COVID-19 have been reported in dense and enclosed environments, research efforts have been focused on aerosol transmission, which is a major mode of infection. Although the literature has traditionally focused on coughing and sneezing, it has become evident that avoiding exposure to the exhaled aerosols of asymptomatic infected persons is important for preventing infection. However, limited experimental cases have investigated ordinary exhaled air in real-world settings. Therefore, the authors of this study visualize the flow of exhaled aerosols with and without masks and face shields by simulating customer service in a beauty salon. Since the particle shape of the exhaled aerosol, which is problematic for infection, is similar to that of the particles released by e-cigarettes, light from a laser source scattered by e-cigarette smoke was captured by a camera. The results suggest that exhaled air flows according to certain rules under the influence of the temperature boundary layer on the human body surface. Therefore, it is evident that masks and face shields control the flow of exhaled air in such scenarios.