If you’re doing a #cosplay that requires a gas mask, you could use an actual gas mask, but it may be cost prohibitive or it may become uncomfortable to wear for long periods as actual gas masks are made with rubber and are intended to form a tight seal around the face. Solution? Make your own cosplay gas mask! Not only will you be able to customize it however you want, it will be very easy to paint! (It’s really not easy to paint stretchy rubber as it will crack when you stretch it or wear it.)
While we aren’t necessarily advocating that you purchase this pattern, but #cosplayer Lost Wax provides an excellent one with a tutorial video on how to make your very own cosplay gas mask: