Daily US Times: Amusement parks are welcoming back visitors, Schools are reopening and outdoor dining is the new way to eat out. But despite the signs that people are returning back to normal life, the coronavirus pandemic has gone nowhere.
That’s why a group of researchers at Duke University created a simple technique to analyze the effectiveness of various types of facemasks which have become a critical component in containing the spread of the virus.
The quest began when a professor at Duke’s School of Medicine was assisting a local group of people buy masks in bulk amount to distribute to community members in need. The professor wanted to make sure the group purchased facemasks that were actually effective to the people.
The study was published on Friday where researchers with Duke’s physics department demonstrated the use of a simple method that uses a laser beam and cell phone to evaluate the efficiency of masks by studying the transmission of respiratory droplets during regular speech.
Martin Fischer, one of the authors of the study, said: “We use a black box, a laser, and a camera”.
“The laser beam is expanded vertically to form a thin sheet of light, which we shine through slits on the left and right of the box.”
There is a hole in the front of the box where a speaker can talk into it. A smartphone camera is placed on the back of the box to record light that is scattered in all directions by the respiratory droplets that cut through the laser beam when they talk.
A simple computer algorithm then counts the droplets seen in the video.
Encouraging the use of effective facemasks
Public health experts have spent months emphasizing that facemasks are one of the most effective tools to stop the spreading of the virus which ultimately help fight the pandemic, and many US states have now introduced some kind of mask requirement.
Researchers discovered that some masks are quite literally useless when testing their effectiveness.
Researchers of the Duke University tested 14 commonly available masks including a professionally fitted N95 mask, usually reserved for health care workers. First the test was performed with a speaker talking without wearing a mask and then they did it again while a speaker was wearing a mask. Each mask was tested 10 times.
The most effective mask was the fitted N95. Cotton masks and three-layer surgical masks and , which many people have been making at home, also performed well.
Neck fleeces were the least effective. These masks are also called gaiter masks and often used by runners. In fact, wearing a fleece mask resulted in a higher number of respiratory droplets because the material seemed to break down larger droplets into smaller particles that are more easily carried away with air.
Knitted masks and folded bandanas also performed poorly and did not offer much protection.
Fischer 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.”
While the setup of the test is quite simple — all that is required is a laser for less than $200, a box, one lens, and a cell phone camera — Fischer does not recommend people to set them up at home.
Unless a person has optic experience or is familiar with laser safety, mishandling powerful lasers can cause permanent eye damage. However, the researchers are hoping companies, community outreach centers and museums will set up the test to show people which masks are the most effective.
Fischer 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.”
Facemasks have become very controvrsial in many countries including the US and Brazil. US President Donald Trump repeatedly denied to wear masks in public places since the pandemic started, until last month he wore one for the first time. He also declined repeated plea to request Americans to wear masks.