One of my guiding principles is that if it's on a roadside sign, it's probably crap. I recall the visceral annoyance I felt when I saw, "It's a small ask!" on signs in Rochester, NY. The most basic, simplistic, engineering analysis on the actions a mask could perform--either a semi-permeable membrane or an impermeable membrane--show it as folly. The lunacy of keeping a nice, warm, bacteria substrate on your mouth and nose? What's the worse that could happen?