Therefore, a group of researchers at Duke University developed a simple technique for analyzing the effectiveness of various types of masks that have become a critical component in stopping the spread of the virus.
The search began when a professor at Duke’s School of Medicine helped a local group buy masks in bulk to distribute to members of the community in need. The professor wanted to make sure the group bought masks that were actually effective.
“We use a black box, a laser and a camera,” Martin Fischer, one of the study’s authors, told CNN. “The laser beam is expanded vertically to form a thin light sheet, which we shine through slits on the left and right sides of the box.”
In front of the box is a hole where a speaker can chat inside. A camera camera is placed on the back of the box to pick up light that is scattered in all directions by the respiratory droplets that cut through the laser beam as they speak.
A simple computer algorithm then counts the drops seen in the video.
Encourage the use of effective masks
Public health experts have insisted for months that masks are one of the most effective tools to help combat the pandemic, and many U.S. states have now introduced one type of mask requirement.
But in testing their effectiveness, researchers discovered that some masks are quite literally useless.
Researchers are testing 14 commonly available masks, including a professionally designed N95 mask, mostly reserved for healthcare workers. First, the test was performed with a speaker speaking without wearing a mask. Then they did it again while a speaker wore a mask. Each mask was tested 10 times.
The most effective mask was the custom N95. Three-layer surgical masks and cotton masks, which many people have made at home, also performed well.
Neck braces, also called gaiter masks and often used by circles, were the least effective. Indeed, wearing a fleece mask resulted in a higher number of respiratory droplets, as the material was found to reduce larger droplets into smaller particles that are more easily removed with air.
Folding bandanas and knit masks also performed poorly and did not offer much protection.
“We were very surprised to find that the number of particles measured with the fleece actually exceeded the number of parts measured without wearing a mask,” Fischer said. “We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”
While the setup of the test is fairly simple – all that is required is a box, a laser for less than $ 200, one lens and a camera for a mobile phone – Fischer does not advise people to set them up at home.
Unless a person is familiar with laser safety or optical experience, mishandling of powerful lasers can cause permanent eye damage. However, the researchers hope that companies, museums and outreach centers for municipalities will institute the test to show people which masks are most effective.
“This is a very powerful visual tool to raise awareness that very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory drops,” Fischer said. “Companies and manufacturers can set this up and test their mask designs before they produce, which would also be very useful.”
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