How far respiratory droplets move in indoor environments?

Abstract

A simple physical model is employed to investigate the coupled evaporation and movement of droplets expelled during respiratory activities, which is essential for studying the transmission route of some respiratory infectious diseases. The exhaled air is treated as a steady non-isothermal jet horizontally issuing into stagnant surrounding and then the droplet is simulated to evaporate and move in this jet. Numerical calculations have been performed for physiological saline droplet, which focus on the study of droplet lifetime and how the droplet size changes, as well as how far the droplet moves. The results indicated that the droplet size predominately decides its evaporation and movement after being expelled. The sizes of the largest droplets that could totally evaporate before falling 2 meters were derived, as well as the maximum horizontal distances that droplets could reach during different respiratory activities. The effect of relative humidity on the dispersal of droplets in air was discussed.