Phosgene gas was first developed by the French in the late 1915. Six days before Christmas, Germans used phosgene gas for the first time during war against the Allied troops. The gas has and odour similar to new mowm hay or grass and a colorless cloud which caught most soldiers off guard, not giving them the chance to defend themselves with gas masks. More than 1,000 soldiers were injured and 120 died. Symptoms of phosgene gas begin immediately. Coughing, sneezing, vomiting, choking, blurred vision, frostbite, burns, or heart failure are seen after exposure. Fluid build up in the lungs leading to death. Some who recover have had results of chronic bronchits and emphysema.
Out of 91,000 deaths from chemical weapons in WWI phosgene gas is responsible for 85% of those deaths.