A home-made cloth face mask must have multiple layers to be effective in preventing the spread of the deadly coronavirus, according to an observational study published in the medical journal Thorax.
Researchers at the University of New South Wales in Australia tried to find out the effectiveness of single- and double-layer cloth face coverings at reducing the spread of respiratory droplets that pass when a COVID-19 infected person speaks, coughs or sneezes. The outcome was then compared with that of a three-ply surgical face mask.
The researchers used LED lighting system and a high-speed camera to film the dispersal of airborne droplets produced by a healthy person with no respiratory infection. The video recording showed that three-ply surgical face mask was the most effective at reducing airborne droplet dispersal.
The single-layer covering reduced the droplet spread from speaking, though the double-layer covering was better in reducing droplets from coughing and sneezing, according to the researchers.
“A cloth face covering with at least two layers is preferable to a single-layer one,” Prateek Bahl of the School of Mechanical and Manufacturing Engineering at UNSW, a lead author of the study, wrote in the findings. “Guidelines on home-made cloth masks should stipulate multiple layers.”
To be sure, the researchers said a single-layer face covering is better than no face covering at all. Additionally, several other factors determine the efficacy of cloth masks such as type of material, the number of layers, the arrangement of different layers and frequency of washing, they said.
The study comes at a time when numbers of COVID-19 cases have seen a sharp jump in many countries. Also, many of them are pushing for the public to adopt face coverings in an attempt to curb the spread of the coronavirus.