Do-it-yourself masks should have several layers - researchers
Do-it-yourself face masks are far more effective at blocking virus-containing droplets if they are made with two or three layers of fabric, researchers advised on Friday in the journal Thorax.
Using high-speed video and special lighting, they saw that when masks have multiple layers, fewer droplets generated by speaking, coughing and sneezing escape, and droplets that do escape do not spread as far.
There is a tradeoff between protection and breathability as the number of layers increases, but "three layers is quite comfortable," study coauthor Raina MacIntyre of UNSW Sydney, in Australia, told Reuters.
For their experiments, her team compared masks made from a single or double layer of T-shirt fabric, which had a thread count of 170/inch.
They also tested a surgical mask.
Freeze frames from the video showed that while the surgical mask was most effective, the two-ply cloth mask did a fairly good job at limiting the distance droplets traveled. Even the one-ply mask was helpful.
"The effectiveness of a mask depends on several factors other than filtration, which is what we tested," MacIntyre added.
"For example, the outer layer should be made of a water-resistant fabric such as polyester," she said. "It is also best to use fabrics with high thread count and fine weave." -- Reuters