Inexpensive, accessible device provides visual proof that masks block
droplets
Study demonstrates a simple way to test facial covering materials for effectiveness

Date:
August 11, 2020
Source:
Duke University Medical Center
Summary:
In a proof-of-concept study, researchers report that a simple,
low-cost technique provided visual proof that face masks are
effective in reducing droplet emissions during normal wear. They
found that the best face coverings were N95 masks without valves --
the hospital-grade coverings that are used by front-line health
care workers. Surgical or polypropylene masks also performed
well. Hand-made cotton face coverings provided good coverage,
eliminating a substantial amount of the spray from normal
speech. But bandanas and neck fleeces such as balaclavas didn't
block the droplets much at all.



FULL STORY ========================================================================== [Person putting on face | Credit: (c) Tanakorn / stock.adobe.com] Person putting on face mask (stock image).

Credit: (c) Tanakorn / stock.adobe.com [Person putting on face | Credit:
(c) Tanakorn / stock.adobe.com] Person putting on face mask (stock image).

Credit: (c) Tanakorn / stock.adobe.com Close 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.


==========================================================================
But he needed to know whether the virus-blocking claims mask suppliers
made were true, to assure he wasn't providing ineffective masks that
spread viruses along with false security. So he turned to colleagues in
the Duke Department of Physics: Could someone test various masks for him? Martin Fischer, Ph.D., a chemist and physicist, stepped up. As director of
the Advanced Light Imaging and Spectroscopy facility, he normally focuses
on exploring new optical contrast mechanisms for molecular imaging,
but for this task, he MacGyvered a relatively inexpensive apparatus
from common lab materials that can easily be purchased online. The setup consisted of a box, a laser, a lens, and a cell phone camera.

In a proof-of-concept study appearing online Aug. 7 in the journal
Science Advances, Fischer, Westman and colleagues report that the simple, low-cost technique provided visual proof that face masks are effective
in reducing droplet emissions during normal wear.

"We confirmed that when people speak, small droplets get expelled,
so disease can be spread by talking, without coughing or sneezing,"
Fischer said. "We could also see that some face coverings performed
much better than others in blocking expelled particles." Notably, the researchers report, the best face coverings were N95 masks without valves
-- the hospital-grade coverings that are used by front-line health care workers. Surgical or polypropylene masks also performed well.



==========================================================================
But hand-made cotton face coverings provided good coverage, eliminating
a substantial amount of the spray from normal speech.

On the other hand, bandanas and neck fleeces such as balaclavas didn't
block the droplets much at all.

"This was just a demonstration -- more work is required to investigate variations in masks, speakers, and how people wear them -- but it
demonstrates that this sort of test could easily be conducted by
businesses and others that are providing masks to their employees or
patrons," Fischer said.

"Wearing a mask is a simple and easy way to reduce the spread of
COVID-19," Westman said. "About half of infections are from people who
don't show symptoms, and often don't know they're infected. They can unknowingly spread the virus when the cough, sneeze and just talk.

"If everyone wore a mask, we could stop up to 99% of these droplets before
they reach someone else," Westman said. "In the absence of a vaccine or antiviral medicine, it's the one proven way to protect others as well
as yourself." Westman and Fischer said it's important that businesses supplying masks to the public and employees have good information about
the products they're providing to assure the best protection possible.



==========================================================================
"We wanted to develop a simple, low-cost method that we could share
with others in the community to encourage the testing of materials,
masks prototypes and fittings," Fischer said. "The parts for the test
apparatus are accessible and easy to assemble, and we've shown that they
can provide helpful information about the effectiveness of masking."
Westman said he put the information immediately to use: "We were trying
to make a decision on what type of face covering to purchase in volume,
and little information was available on these new materials that were
being used." The masks that he was about to purchase for the "Cover
Durham" initiative? "They were no good," Westman said. "The notion that 'anything is better than nothing' didn't hold true."

========================================================================== Story Source: Materials provided by Duke_University_Medical_Center. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* YouTube:_Inexpensive_way_to_test_face_mask_effectiveness_in_reducing
COVID-19_transmission ========================================================================== Journal Reference:
1. Emma P. Fischer, Martin C. Fischer, David Grass, Isaac Henrion,
Warren S.

Warren, Eric Westman. Low-cost measurement of facemask efficacy
for filtering expelled droplets during speech. Science Advances,
August 7, 2020; DOI: 10.1126/sciadv.abd3083 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200811152916.htm

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