Researchers from the Universities of Bristol and Surrey have found that well-fitting, three-layered cloth masks can be as effective at reducing the transmission of COVID-19 as surgical masks.
The team looked at how liquid droplets are captured and filtered out in cloth masks by reviewing and modelling filtration processes, including inertial impaction.
Inertial impaction does not filter as a sieve or colander does—it works by forcing the breath to twist and turn inside the mask so much that the droplets cannot follow the path of the air. Instead, the droplets crash into fibres inside the mask to prevent inhalation.
The team found that, under ideal conditions and dependent on the fit, three-layered cloth masks can perform similarly to surgical masks for filtering droplets—with both reducing the exposure by around 50 to 75 per cent. If an infected person and a healthy individual are both wearing masks, this could increase to 94 per cent.
Dr Richard Sear, co-author of the study and leader of the Soft Matter Group at the University of Surrey, said: "While wearing a simple and relatively inexpensive cloth face mask cannot eliminate the risk of contracting COVID-19, measurements and our theoretical model suggests they are highly effective in reducing transmission."
