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N95 mask warning
A real bummer.
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Why your N95 mask could endanger others
A feature that makes breathing easier increases infection risk
By Mike Moffitt, SFGATE
To shop in a store or ride public transit, San Franciscans must now wear a face covering. But before you roll a cart into the Safeway, check your mask.
Does it have an external one-way valve about the size of a quarter? If so, you could be barred from entry.
The valves, typically found on some N95 respirator masks to make breathing easier, are not allowed under the city’s most recent COVID-19 mask directive.
At first glance, that seems counterintuitive. A 2008 study by scientists in the Netherlands found that well-fitted N95 masks provided adults with about 50 times as much protection as home-made masks and roughly 25 times as much as surgical masks.
However, if an N95 mask has an external valve, it does an inadequate job of protecting others who come near the wearer. If that person should cough or sneeze through the valve, unfiltered droplets could travel through the opening and potentially contact anyone in range, according to the San Francisco Department of Health.
Health care workers use two kinds of N95 masks — surgical respirators (for working in a sterile field) and N95 respirators without valves. These masks have been in short supply and should only be worn by doctors, nurses, first responders and other health care workers, according to the Centers for Disease Control and Prevention.
The masks are valued so much at Zuckerberg San Francisco General Hospital that nurses will wear surgical (cloth) masks over their N95 masks so the latter will stay cleaner and last longer.
Many San Franciscans still have valved N95 masks that they picked up during the 2017 wildfires lying around. Are they now useless?
San Francisco Firefighters Local 798 tweeted a video showing how an N95 mask with an external valve can be salvaged for pandemic use by simply putting a surgical mask or other cloth mask over it.
Imported N95 masks have been flooding the U.S. market during the pandemic, and many do not meet certification standards, according to the Wall Street Journal. The report noted that tests by the National Institute for Occupational Safety and Health (NIOSH) found that 60% of 67 different kinds of the masks allowed in more tiny particles in at least one sample than U.S. standards normally permit.
N95 respirators certified by NIOSH filter at least 95% of airborne particles.
https://www.sfgate.com/living-in-sf/...s-15246318.php