The article is in the Wall Street Journal.
But first here are some stats from the BBC – the death rates per million from COVID in three countries:
Great Britain – 600/1,000,000
United States – 400/1,000,000
Japan – 7/1,000,000
That's right, Japan has phenomenally fewer deaths and virtually everyone wears a mask in public. That has to be a factor, although perhaps not the only one.
Here's the WSJ article – unfortunately the useful graphs couldn't be transferred over …
The study found that aerosol-size droplets expelled from the mannequin with the double-layered cotton mask traveled forward about 2.5 inches on average, and that most of the leakage escaped from gaps between the nose and face. Loosely fitting facial coverings, including a folded cotton handkerchief with ear loops, as well as a bandanna were less helpful, the study found. With those masks, droplets traveled on average about 1.25 and 3.5 feet, respectively. In contrast, the study found droplets traveled about 8 inches on average with an off-the-shelf cone-shaped mask.
Meanwhile, droplets from an uncovered cough traveled around 8 feet on average, though the study found that they could travel up to 12 feet—double the currently recommended social-distancing guideline of 6 feet. Leakage from a common disposable surgical mask wasn’t studied, though two of the study’s authors, Siddhartha Verma and Manhar Dhanak, said they are working on it.
“It was surprising in a good way to see that a homemade mask could do so well…that we don’t have to get a very fancy mask,” Dr. Verma said. “A cotton mask can be washed at home and dried. Reusability is becoming important as we go into this for the long haul.”
Yay to double layered at home stuff – that's what we use.
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