Time to start sewing....
https://edition.cnn.com/2020/04/02/health/aerosol-coronavirus-spread-white-house-letter/index.html (CNN)A prestigious scientific panel told the White House Wednesday night that research shows coronavirus can be spread not just by sneezes or coughs, but also just by talking, or possibly even just breathing. "While the current [coronavirus] specific research is limited, the results of available studies are consistent with aerosolization of virus from normal breathing," according to the letter, written by Dr. Harvey Fineberg, chairman of a committee with the National Academy of Sciences.
Fineberg told CNN that he will wear start wearing a mask when he goes to the grocery store. "I'm not going to wear a surgical mask, because clinicians need those," said Fineberg, former dean of the Harvard School of Public Health. "But I have a nice western-style bandana I might wear. Or I have a balaclava. I have some pretty nice options."
[For those not familiar, the National Academy of Sciences are some of the top brains going, pretty much, in the USA. You have to be significantly advanced in your career as a scientist and have a significant body of important work on your CV to be inducted into the group.]
There was a choir in Washington State (I think - might have been Oregon?) where nobody had symptoms. They all went to choir practice. But someone was a carrier, and there are now dead choir members and most of the rest of the choir is ill. While singing does have you expelling a lot more air from your lungs than a normal conversation, who's taking chances?
I believe I read somewhere that cotton t-shirt material will block 75% of aerosolized particles that are actually smaller than the Covid. So I would assume a double layer would be a good idea. It won't be as good as a N-95 mask, but healthcare providers need those. I believe I read that vacuum cleaner bags filter more thoroughly, but it's difficult to breath through a vacuum cleaner bag. It's also difficult to breathe comfortably through a lot of synthetics for significant periods of time. Cotton you can throw in a screaming hot washing machine with bleach.