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Researchers created a test to determine which masks were the least effective



That is why a team of researchers at Duke University created a simple technique for analyzing the effectiveness of masks that have become a key ingredient in preventing the spread of virus.

The mission began when a professor at Duke School of Medicine was assisting a local group in buying masks in bulk to distribute them to community members in need. Professor wants to make sure the group bought the mask that is really effective.

In research published Friday, researchers from Duke’s physics department demonstrated using a simple method that uses laser beams and a cell phone to evaluate the effectiveness of the mask. by studying the transmission of respiratory droplets during normal speech.

“We use black boxes, lasers and cameras,”

; Martin Fischer, one of the study’s authors, told CNN. “The laser beam is extended vertically to form a thin sheet of light, we shine through the slits on the left and right sides of the box.”

In the front of the box is a hole for the speaker to talk into. A cell phone camera is placed on the back of the box to record light scattered in all directions by respiration droplets cut through the laser beam as they speak.

Then a simple computer algorithm will count the drops seen in the video.

Encourage the use of effective masks

Public health experts have spent months emphasizing that masks are one of the most effective tools to help fight a pandemic, and many US states now have a number of masking requirements in place.

But when testing their effectiveness, the researchers found that some masks were literally completely useless.

Researchers tested 14 commonly available masks, including a professionally equipped N95 mask, usually intended for medical personnel. First, the test was done with a speaker who spoke without a mask. Then, they do it again while a speaker is wearing a mask. Each mask was tested 10 times.

The most effective mask is the N95 fitted. Triple masks and cotton masks that many people make at home also work well.

14 masks were used in the test.

The neck patch, also known as a runner’s mask and commonly used by runners, is the least effective. In fact, wearing a fleece mask results in a higher number of respiration drops as the material appears to decompose larger droplets into smaller particles that are easier to carry with air.

Folds and knitted masks also perform poorly and provide not much protection.

“We were surprised to find that the number of particles measured with wool actually exceeded the number of particles measured without wearing any masks,” Fischer said. “We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that really work.”

While the test’s setup is pretty straightforward – all that’s needed is a box, a laser for under $ 200, a lens and a phone camera – Fischer doesn’t recommend setting up. they are at home.

Unless a person has a clear understanding of laser safety or has vision experience, the mishandling of a strong laser could cause permanent eye damage. However, researchers are hoping companies, museums and outreach centers will set up experiments to show people what masks are most effective.

“This is a very powerful visual tool for raising awareness that a very simple mask, like this homemade cotton mask, is actually effective at suppressing most respiratory drops,” Fischer said. this. “Companies and manufacturers can set this up and test their mask designs before production, which would also be very helpful.”


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