@melaninpony few different designs about

Most appropriate I think is probably the Olson Mask ( https://www.regmedctr.org/webres/File/OlsonMask_wPattern_v3-USE%20THIS%20ONE.pdf ) but that does ideally need a 0.3 micron filter fitted to it

Second is from the Cuban ministry of health, surgical mask style, video in spanish but easy enough to follow if you don't speak it ( https://www.youtube.com/watch?v=cw0zLTyU53o )

And he's a bodge job from the US surgeon general ( https://www.youtube.com/watch?v=tPx1yqvJgf4 )