After months of telling vaccinated Americans that it was fine to not wear masks in public spaces indoors, the CDC has updated its guidelines for mask-wearing.
the CDC recommends vaccinated individuals wear masks indoors in public if they live in an area with high Delta transmission rates.
Some public health experts outside the CDC have been advising since late 2020 that everyone keep wearing masks, regardless of vaccination status.
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We know masks work to slow the spread of Covid-19 — when they’re worn properly.
But sometimes it helps to see why.
Phyics of Fluids/Matthew Staymates
Masks with plastic valves on the outside allow higher airflow, but may also allow more particles in or out. It’s probably best to avoid them altogether.
Not only does the type of mask you wear matter, but how you wear it.
One demonstration from the University of New South Wales shows how different mask materials block coughs and sneezes.
Even just talking releases small particles of spit in the air.
Emma Fischer, Duke University/Science Advances
But, as researchers from Duke University demonstrated in 2020, both medical and homemade, cloth masks can stop the spread of potentially Covid-19-causing particles.
Gaiters and bandanas, however, offer very little protection.
It’s really not a replacement for mask-wearing.
This demonstration, which was part of a study published in Physics of Fluids, shows the increased airflow under a face shield. Smaller aerosols can escape, as well.
While they might protect you from someone’s spit spray, shields won’t be a catch-all for particles like a properly-fitted face mask.
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