Table I.

The Fate of Respiratory Droplets by Size at 20°C and 50% Relative Humidity

Original size	Estimated final size	Fate of droplets at 20 °C and 50% relative humidity
1 mm	350 µm	Sneezing produces droplets of this size. These droplets are not aerosols but are comparable in size to raindrops and would settle in 0.4 seconds.
100 µm	35 µm	A 100 µm droplet will settle in six seconds.
10 µm	3.5 µm	Coughing produces droplets of this size, which evaporate in 0.2 seconds to 3.5 µm droplet nuclei. The nuclei would theoretically require one hour to settle in still air, but in practice are entrained in air currents.
5 µm	1.8 µm	Speaking produces droplets of this size, which evaporate in 0.1 seconds to 1.8 µm droplet nuclei. The nuclei would theoretically require four hours to settle in still air, but in practice are entrained in air currents.
0.8 µm	0.3 µm	Breathing produces droplets of this size, which evaporate in a few milliseconds to 0.3 µm droplet nuclei (comparable in size to smoke particles). The nuclei would theoretically require 20 hours to settle in still air, but in practice are entrained in air currents.