Duke University Study Rates Best and Worst Face Masks

Ruben Fields
August 11, 2020

New research authored by a group of scholars at Duke University in the U.S. compared 14 different types of masks to see which ones would be the most effective at reducing the spread of the coronavirus.

The researchers further mentioned in their report that the most effective way to cover face is to use N95 masks without valves - the hospital-grade coverings that are used by front-line healthcare workers. However, bandanas and neck fleeces didn't block the droplets much at all and barely performed better than no mask.

Researchers have devised a test for face masks to show which are the best at blocking droplets of fluid - and rated several current options. Viral particles can be carried by these droplets, spreading the virus. He added: "We could also see that some face coverings performed much better than others in blocking expelled particles".

To fill that void, Fischer and his team devised an easy-to-make, cheap laser experiment, which can be used to test how different kinds of masks block tiny droplets that come out of people's mouths when they speak.

"The focus of the study was to develop a simple technique for mask testing that people could duplicate and set up themselves", he said.

"We certainly encourage everyone to wear a mask, but we want to make sure that when you wear a mask and you go to the trouble of making a mask, you make one, or wear one that actually helps not just you, but helps everyone". Surgical masks came in second with one per cent.

Martin Fischer, Ph.D., a chemist and physicist, stepped up.

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"If everyone wore a mask, we could stop up to 99 per cent of these droplets before they reach someone else", Westman said. Knitted mask. 4. Two-layer polypropylene apron mask. 5. But there is a caveat.

But improvised face coverings such as bandanas and balaclava-style face coverings were less effective, the researchers found. Reasons have included: (1) we don't truly know that cloth masks (face coverings) are not effective, since the data are so limited, (2) wearing a cloth mask or face covering is better than doing nothing, (3) the article is being used by individuals and groups to support non-mask wearing where mandated and (4) there are now many modeling studies suggesting that cloth masks or face coverings could be effective at flattening the curve and preventing many cases of infection. It noted that due to a global shortage of commercial supplies, there was widespread use of homemade masks and mask alternatives.

Duke physician Eric Westman was one of the first champions of masking as a means to curtail the spread of coronavirus, working with a local non-profit to provide free masks to at-risk and under-served populations in the greater Durham community. They can unknowingly spread the virus when the cough, sneeze and just talk. "There are many people out there that don't know that they're infected, and the face coverings are one way to give people the assurance that there is some source control going on", says Adalja.

The findings are reported in Science Advances.

The time evolution of the droplet count (left axis) is shown for representative examples, marked with the corresponding color in (A): No mask (green), Bandana (red), cotton mask (orange), and surgical (blue - not visible on this scale).

Duke researchers created an low-cost mask-testing apparatus from common lab materials that can easily be purchased online.

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