What is the protective value of different face masks?

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ISLAMABAD, December 17 (online): Researchers have assessed how effective various medical and consumer-grade masks are at protecting the wearer from exposure to particles similar in size to SARS-CoV-2.
This explains a fundamental way in how the virus spreads: being ejected from a person with the infection via their nose or mouth as they talk, sing, sneeze, or cough. Wearing masks to interrupt this route of transmission has been increasingly recommended by scientists, clinicians, and government agencies.
“cloth face coverings are one of the most powerful weapons we have to slow and stop the spread of the virus — particularly when used universally within a community setting.”
“All Americans have a responsibility to protect themselves, their families, and their communities,” he emphasizes.
Experts believe face masks effectively reduce viral transmission because they block a person from expelling the virus and help prevent a person from receiving the expelled virus.
A particle generator filled the exposure chamber with particles of sodium chloride ranging in size from 0.02–0.60 micrometers (mcm) — slightly smaller than those of SARS-CoV-2, which range from 0.06–0.14 mcm.
Each of the tested masks had a sampling port installed, enabling the scientists to compare sodium chloride concentrations behind the masks against the concentration in the general atmosphere of the exposure chamber.
The researchers instructed an adult male without a beard to wear the masks. As part of the testing, the team asked him to perform a series of movements of his facial muscles, head, and torso, following the recommendations of the Occupational Safety and Health Administration Fit Testing Protocol.
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