Developed by Britain in 1916, The PH Hood was worn in conjunction with a Protective Helmet. Chemical Warfare (Gas Agents), had been introduced into the battlefield. Deployed by artillery shells, soldier had but seconds to don protective headgear. Mustard, Chlorine and a host of other deadly clouds of chemicals were deployed (by all sides) – into the already deadlocked morass that was known as Trench Warfare. Known technically as The Phenate Helmet they were designed out of one piece of heavy leather or canvas. 2 large glass viewing lens were sewed into the front. A leather “breathing tube” with a small filter was added. Over 1 million PH Devices were constructed for use in The War. It would be replaced by The M2 Gas Mask in 1917.