April 8, 2021

Better masks, ventilation needed to curb spread of COVID-19 in enclosed spaces

By: Judy Mathias

Editor's Note

Findings in this study, by researchers at the Indian Institute of Technology Bhubaneswar, show the need for new mask designs that reduce side and bottom droplet leakage and good ventilation systems that take into account the aerosolized particle leakage that occurs with breathing and normal conversation as a way to reduce the spread of COVID-19 in enclosed spaces.

In an experimental setup, researchers connected a mechanical breathing simulator to a 5 foot 8 inch mannequin, and they filled a fog generator with water and glycerin to emulate saliva droplets. Droplet exposure was illuminated and captured by video camera.

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Among the findings:

  • with no face covering, droplets from normal breathing can travel up to 4 feet in 5 seconds
  • two-layer homemade and commercial cotton masks were unable to impede the leakage of droplets in the forward direction; addition of a face shield helped prevent leakage and diffusion of droplets
  • a commercial five-layered mask provided the best full front-of-face protection with minimal leakage below the chin
  • a commercial N-95 mask impeded droplet leakage in front, but leakage in gaps between the mask and nose was significant
  • leakage of droplets from the front of a surgical mask was evident; adding a face shield stopped leakage in the forward direction, but settling of droplets below the face shield was noticeable.

The researchers say the findings show that social distancing is equally important as mask wearing when people indoors are just breathing or participating in normal conversation. The findings also show the need for good ventilation systems that take into account the 5% to 10% of aerosolized particle leakage that occurs when just breathing as a way to reduce droplet concentration in enclosed spaces.

The researchers note that the noticeable droplets settling below the face shield is concerning, and pairing surgical masks with shields is not adequate in hospitals and other places where strict social distancing guidelines are difficult to follow.


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