Breathing, virus transmission, and social distancing—An experimental visualization study

Abstract

With the outbreak of COVID-19 in many countries, public awareness related to the droplet mode of virus transmission is well documented and communicated. With a large spike in COVID-19 positive cases and the mortality rate, most of the general public are following preventive measures such as wearing masks, maintaining social distancing, and frequent hand washing. However, recently, it has been reported that the virus may also transmit through aerosolized particles of diameter <10 µm. The majority of the past research focuses on understanding droplet generation and transport through the most violent spasmodic expiration: coughing and sneezing. However, “breathing,” the most common phenomenon, is scarcely studied as a virus transmission source. In the present study, we report an experimental visualization of the droplet’s transport through breathing to quantify the reach of a typical breath for various exhale to inhale ratios. The efficacy of various standard (surgical, five-layered, and N95) and non-standard (homemade) protective measures such as face masks and face shields is also evaluated. An exhaled breath at E:I = 1:1 can travel up to 4 ft in 5 s; however, this reach reduces to 3 ft for E:I = 1:2. Two-layer homemade and commercial cotton masks are unable to completely impede the leakage of the droplet in the forward direction. A combination of a two-layer mask and face shield is also not effective in preventing the leakage and diffusion of the droplets. The surgical mask alone is not recommended during normal conversations as the leakage of the droplets is noticeable. A commercial N95 mask completely impedes the leakage of the droplets in the forward direction. However, the leakage of the droplets from the gaps between the mask and the nose is observed to be significant. A commercial five-layered mask is observed to be the most effective preservative measure with minimum leakage of the droplets.