Experimental visualization of expiratory diffusion under face-to-face situation with utterance

Due to the influence of the COVID-19, great damage has occurred all over the world. Not only health and medical problems, but also the effects of the decline in quality of life and economic activity due to the suspension of social activities cannot be ignored. It is thought that the main cause of virus infection is coughing and sneezing, but in recent it has become a topic that there is a possibility of airborne infection by aerosols containing viruses scattered in the air. In the case of airborne infection, the risk of infection is considered to increase when the mucous membrane is exposed to exhaled aerosol for a long time. Therefore, in this study, we actually visualized human breath by using the smoke of electronic cigarettes as tracer particles. For 4 patterns of the human posture, exhaled breath was visualized. As a result, it was clarified that the exhaled breath is affected by the body wall temperature and rises when it stays in the boundary layer, falls when it leaves, or diffuses randomly. This finding is effective in reducing the risk of infection during face-to-face customer service, and is considered to be the first discussion of the characteristics of human exhalation affected by temperature.