Why do most military gas masks use 2 lenses while civilian ones used by firefighters or commercial full face respirators use a single piece face plate? - Quora
![Gas Warfare in the First World war: Gas Masks and Gas Defence Equipment of the Armies of the German Empire, Austria-Hungary and Italy by Egidio Rossi; Marco Pisani; Andrea Brambilla; Ariberto Osio: Gas Warfare in the First World war: Gas Masks and Gas Defence Equipment of the Armies of the German Empire, Austria-Hungary and Italy by Egidio Rossi; Marco Pisani; Andrea Brambilla; Ariberto Osio:](https://pictures.abebooks.com/isbn/9783903341173-us.jpg)
Gas Warfare in the First World war: Gas Masks and Gas Defence Equipment of the Armies of the German Empire, Austria-Hungary and Italy by Egidio Rossi; Marco Pisani; Andrea Brambilla; Ariberto Osio:
![Gas masks of second world war displayed on street for tourists as souvenir 2548553 Stock Photo at Vecteezy Gas masks of second world war displayed on street for tourists as souvenir 2548553 Stock Photo at Vecteezy](https://static.vecteezy.com/system/resources/previews/002/548/553/large_2x/gas-masks-of-second-world-war-displayed-on-street-for-tourists-as-souvenir-photo.jpg)