Using a bandana as a face covering is not effective, researchers have found - but your homemade cotton face mask could be doing a very good job.
Researchers from Duke University have looked into how effective different types of mask are.
They looked at 14 different face masks, ranging from homemade cotton ones to heavy-duty ones designed for medical professionals.
The study's co-author Isaac Henrion spoke to Moncrieff about what they found.
He explained: “It’s important to be clear about what this study was: we’re showing a new technique for measuring how effective face coverings are for stopping those droplets.
“We did find one - a kind of neck gaiter made of a thin and stretchy fabric - wasn’t very effective at all, and that’s probably because of the fabric being so thin.
“There’s a lot of consistency in the [other] different masks that we tested. A two-layer cotton mask - which people are making at home - was really effective. We tested a bunch of them, and they were all effective.
“It’s quite easy to tell if it’s going to be good or not. Can you stretch it, put it up to the light and see through it? Then it’s probably not going to be good.”
Types of masks
According to the study - the results of which have been published in the Science Advances journal - the mask alternatives such as a neck fleece or bandanas offer very little protection.
Mr Henrion explained the researchers also tested one professionally fitted N95 mask without a valve, and that stopped almost all the air droplets.
A standard blue surgical procedure mask - the disposable ones which have become commonplace in recent months - were also really effective.
He explained: “Coming in just behind, you have those two layer cotton masks as people are making at home - they were almost as effective as a surgical mask.
“Right at the end, you had one or two made of flimsy material.
"I’d emphasise that the majority of homemade masks that we tested, as well as the ones made by factories and companies… they all worked really well.”
In terms of the N95 mask, Mr Henrion sounded a note of caution for those who might be considering wearing them for everyday use.
He said: “They’re really reserved for healthcare professionals… they are a tight seal around the face. They’re quite uncomfortable to wear: you don’t really want to wear it all day if you don’t have to.
“A simple two-layer cotton mask was stopping 80% or even more of the particles getting out. That’s really what we need - if we all do it, that’s going to reduce transmission, no doubt.”
Mr Henrion stressed that the primary purpose of wearing face masks is to protect other people.
He said: “There may be some protection to the wearer, but primarily it’s about stopping those tiny droplets that come out of your mouth when you speak.
“If we can stop those droplets before they get out into the environment, we can reduce the risk of coronavirus transmission."