Replicated cough confirms efficacy of multilayer mask

Face masks have been worn throughout the COVID-19 pandemic to keep infectious respiratory droplets at bay. While previous studies have focused on how single droplets interact with masks, Vadlamudi et al. studied a spray of droplets that more closely replicates a cough or sneeze.

The spray, which contained virus-sized nanoparticles, consisted of various droplet sizes and velocities to mimic a cough. The authors used high-speed shadowgraphy to examine how this cough-like spray interacted with masks of varying porosity, pore size, and thickness. They found a multilayered mask best stops the spread of droplets from an infected individual.

Their results showed that if an infected person and non-infected, susceptible person are each wearing a single-layer mask and within conversational distance, the spray droplets can exit the infected person’s mask and penetrate the susceptible person’s mask. This suggests both multilayer masks and social distancing are necessary to prevent infection.

“In a pandemic like COVID-19, a mask seems to be too simple of a solution to the problem,” said author Saptarshi Basu. “However, the fact is that a mask, along with other protocols like social distancing and sanitization, can prevent a pandemic.”

This work also demonstrated that, at high enough velocities, spray droplets of all sizes can penetrate mask fabric and atomize into smaller droplets called aerosols. Aerosols are especially dangerous because they have a longer airborne lifetime. Future research must further study these aerosols to better understand how a real virus-laden cough interacts with masks.

Source: “Penetration and aerosolization of cough droplet spray through face masks: A unique pathway of transmission of infection,” by Gautham Vadlamudi, S. K. Thirumalaikumaran, Dipshikha Chakravortty, Abhishek Saha, and Saptarshi Basu, Physics of Fluids (2022). The article can be accessed at https://aip.scitation.org/doi/full/10.1063/5.0093297 .

This paper is part of the Flow and the Virus Collection, learn more here .