I got one of their FF400 face shield respirators to do lead paint removal and spent dozens of hours in unconditioned spaces with a tyvek suit. They are extremely well designed and never fog because the inhaled air passes first through the face mask area and then through one-way valves into the mouth/nose section and is exhausted downward at the front of the mouth/nose area.
I used it during the beginning of COVID to protect myself up until I was vaccinated and went for about 18 months before getting infected. Definitely got some odd looks at Costco.
Maybe you are meaning for medical staff? Yeah there's a fully unfiltered exhaust stream blowing downwards.
