hard to find original early 1940's american vintage industrial portable chlorine gas mask fabricated by or for the mine safety appliance company, pittsburgh, pa. the original reinforced carrying and/or storage case with instructions is included. chlorine gas, also known as bertholite, was first used as a weapon in world war i by germany on april 22, 1915 in the second battle of ypres. as described by the soldiers it had a distinctive smell of a mixture between pepper and pineapple. it also tasted metallic and stung the back of the throat and chest. chlorine can react with water in the mucosa of the lungs to form hydrochloric acid, an irritant that can be lethal. the damage done by chlorine gas can be prevented by a gas mask, or other filtration method, which makes the overall chance of death by chlorine gas much lower than those of other chemical weapons. it was pioneered by a german scientist later to be a nobel laureate, fritz haber of the kaiser wilhelm institute in berlin, in collaboration with the german chemical conglomerate ig farben, who developed methods for discharging chlorine gas against an entrenched enemy. the rubber mask containing oversized glass eye lenses is comprised largely of black rubber. the hoses, straps and canister are intact and unused. salvaged from a chicago area chemical plant. case measures 9 x 15 x 13 inches.