Have you been questioning the need of wearing face-mask amid pandemic? A study by researchers at the Indian Institute of Technology, Powai, shows how important it is. The study finds out, while the cloud of cough remains effective till about 8 seconds before dissipating irrespective of whether the person is masked or not, surgical masks reduce the volume by seven times compared to having no mask.

By analysing the equations of flow for the cough, the researchers found that a large volume of ambient air slowly gets trapped inside the cloud as it spreads outwards. With time, the droplet concentration inside the cloud thus reduces significantly from its initial concentration. Since the virus requires liquid droplets to survive, the possibility of its spread declines. They also found that the front of the cough cloud covers the first two metres of its total distance from the source within two seconds of being emitted. Hence, the cloud has the maximum probability of spreading the viral liquid immediately after release. The study was published in the journal, Physics of Fluids.