SCIENTISTS have carried out tests on 14 different styles of face masks and discovered that some actually increase the risk of Covid-19 infection.
Researchers at Duke University in North Carolina studied everything from protective covering used by doctors to bandanas and knitted masks.
Best performer: N95 masks which are used by healthcare professionals in the US came out top in the study.
The experts found that the coverings worked best at stopping the transmission of respiratory droplets when users were speaking.
Next best: Three-layer surgical masks and cotton masks, which can be made at home, also performed well at stopping the spread of the deadly coronavirus.
Worst performer: Neck fleeces, also known as gaiter masks or snoods, were the least effective at stopping the transmission.
Often used by runners, the covering resulted in a higher number of respiratory droplets because the material broke down large droplets into smaller particles which are then spread more easily into the air.
Next worst: Knitted masks and bandanas also did not provide much protection, Duke’s physics department found.
Martin Fischer, one of the study’s authors, told CNN that wearing a neck fleece actually increases the risk of infection.
He said: “We were extremely surprised to find that the number of particles measured with the fleece actually exceeded the number of particles measured without wearing any mask.
“We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”
The test which the research team used involved a black box fitted with a laser and a cell phone camera.
A face mask-wearer would then speak inside the box into the direction of the laser and the the respiratory droplets would then be recorded by the camera.
The amount of droplets would then be counted by a computer algorithm.
Fischer said the test was relatively simple and could be used by face masks companies.
He said: “This is a very powerful visual tool to raise awareness that a very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory droplets.
“Companies and manufacturers can set this up and test their mask designs before producing them, which would also be very useful.”