When One type of poison gas (mustard gas) gets in contact, the follow things happen. You eyes will inflammation and even blindness. Your skin will build yeLlow blisters, and if you are luck will only vomit. It is unlikely to survive a gas attack.
Nerve gases attack the body’s nervous system. The symptoms are nausea, vomiting, muscular twitching, convulsions, cessation of breathing and death
Can spread enough to kill the occupants of 30 cities the size of Paris.