Comparing face coverings in controlling expired particles
Surgical, N95 masks block most particles, study finds

Date:
September 25, 2020
Source:
University of California - Davis
Summary:
Laboratory tests of surgical and N95 masks show that they do cut
down the amount of aerosolized particles emitted during breathing,
talking and coughing. Tests of homemade cloth face coverings,
however, show that the fabric itself releases a large amount of
fibers into the air, underscoring the importance of washing them.



FULL STORY ========================================================================== Laboratory tests of surgical and N95 masks by researchers at the
University of California, Davis, show that they do cut down the
amount of aerosolized particles emitted during breathing, talking and
coughing. Tests of homemade cloth face coverings, however, show that
the fabric itself releases a large amount of fibers into the air,
underscoring the importance of washing them. The work is published
Sept. 24 in Scientific Reports.


==========================================================================
As the COVID-19 pandemic continues, the use of masks and other face
coverings has emerged as an important tool alongside contact tracing
and isolation, hand- washing and social distancing to reduce the spread
of coronavirus. The CDC and the World Health Organization endorse the
use of face coverings, and masks or face coverings are required by many
state and local governments, including the state of California.

The goal of wearing face coverings is to prevent people who are infected
with COVID-19 but asymptomatic from transmitting the virus to others. But
while evidence shows that face coverings generally reduce the spread
of airborne particles, there is limited information on how well they
compare with each other.

Sima Asadi, a graduate student working with Professor William Ristenpart
in the UC Davis Department of Chemical Engineering, and colleagues at
UC Davis and Icahn School of Medicine at Mount Sinai, New York, set up experiments to measure the flow of particles from volunteers wearing
masks while they performed "expiratory activities" including breathing, talking, coughing and moving their jaw as if chewing gum.

Asadi and Ristenpart have previously studied how people emit small
particles, or aerosols, during speech. These particles are small enough
to float through the air over a considerable distance, but large enough
to carry viruses such as influenza or coronavirus. They have found that
a fraction of people are "superemitters" who give off many more particles
than average.

The 10 volunteers sat in front of a funnel in a laminar flow cabinet. The funnel drew air from in front of their faces into a device that measured
the size and number of particles exhaled. They wore either no mask,
a medical-grade surgical mask, two types of N95 mask (vented or not),
a homemade paper mask or homemade one- or two-layer cloth mask made from
a cotton T-shirt according to CDC directions.



==========================================================================
Up to 90 percent of particles blocked The tests only measured outward transmission -- whether the masks could block an infected person from
giving off particles that might carry viruses.

Without a mask, talking (reading a passage of text) gave off about 10
times more particles than simple breathing. Forced coughing produced a
variable amount of particles. One of the volunteers in the study was a superemitter who consistently produced nearly 100 times as many particles
as the others when coughing.

In all the test scenarios, surgical and N95 masks blocked as much as
90 percent of particles, compared to not wearing a mask. Face coverings
also reduced airborne particles from the superemitter.

Homemade cotton masks actually produced more particles than not wearing
a mask.

These appeared to be tiny fibers released from the fabric. Because the
cotton masks produced particles themselves, it's difficult to tell if
they also blocked exhaled particles. They did seem to at least reduce
the number of larger particles.

The results confirm that masks and face coverings are effective in
reducing the spread of airborne particles, Ristenpart said, and also
the importance of regularly washing cloth masks.

Additional co-authors on the study are Christopher Cappa, Santiago
Barreda and Anthony Wexler at UC Davis; and Nicole Bouvier, Icahn School
of Medicine at Mount Sinai, New York. It was supported by a grant from
the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.


========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Andy Fell. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* YouTube_video:_Testing_a_Surgical_Face_Mask ========================================================================== Journal Reference:
1. Sima Asadi, Christopher D. Cappa, Santiago Barreda, Anthony
S. Wexler,
Nicole M. Bouvier, William D. Ristenpart. Efficacy of masks and
face coverings in controlling outward aerosol particle emission
from expiratory activities. Scientific Reports, 2020; 10 (1) DOI:
10.1038/ s41598-020-72798-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200925113650.htm

--- up 4 weeks, 4 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)