Interpersonal droplet transmission risk and countermeasures in thermally stratified environment

Thousands of patients with COVID-19 share the same space with medical staff in the makeshift hospital and contact with each other frequently, which may be a risk of nosocomial infection. The downward wall jet along the inner glass facade is likely to cause thermal stratification under winter conditions. Utilizes two full-scaled numerical models to simulate the dispersion of expiratory droplets under typical thermal stratification conditions by the CFD method. By counting the number of droplets inhaled by the susceptible, combined with the laboratory result, quantifies the risk of interpersonal droplet transmission. It is found that the number of inhaled droplets by the susceptible decreases by more than 60%, when the vertical temperature gradient decreases from 1.50 K/m to 1.08 K/m within a mutual distance of 1 m. Therefore, it is necessary to increase ventilation rate, and locate heaters under the inner side of glass facade to diminish downward wall jets, avoid the formation of vertical temperature stratification, and dilute the concentration of droplets in occupied zone, which effectively reducing the risk of cross infection.