The gas mask was developed early in WW1 in 1915 to protect the soldiers from poisonous gas. Some examples of the poison gas is tear gas which would cause temporary blindness and that was used by the French. Chlorine gas which was first used by the Germans. It destroys the respiratory system leading to a slow and painful death. Mustard Gas was the most deadly out of all of the gasses because it was odorless and colorless making it completely undetectable. It only took 12 hours to take effect. If infected by the mustard gas, your skin will blister, and cause internal bleeding. People would begin to die in 4-5 weeks. Mustard gas was invented by the Germans in 1917