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
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Child's Gas Mask, World War II, Original | Object Lessons - Conflict & Protest: 20th Century - Present
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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:
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