"Things You Wouldn't Know If We Didn't Blog Intermittently."
Great explanation of "how it works" ~ TFS!
And to Peter Bear I think it was, sorry. I was so quickly deleting spam comments that I accidentally deleted yours. My bad.
about sarah little turnbull, the designer whose work led to the development of the N95 respirator: https://www.metropolismag.com/design/sara-little-turnbull-corporate-americas-secret-weapon/ Sara Little Turnbull, Corporate America’s Secret WeaponI-)
All I know is that they're damn hard to breathe out of with the slightest exertion.