Face masks with plastic device on front are probably worthless.

[Warpy]

5. Thank you very much

I worked in health care, so I haven't seen such masks. I imagine they're used in industrial settings where nanoparticulates are the problem, not contagion. I can see that they'd work very well for people like miners and welders, increasing comfort when worn over a long period of time.

N-95 masks and OR respirators get distinctly swampy very quickly. While they're freely gas permeable, people who aren't used to them feel like they're suffocating as their air gets hot and wet.