Poison Gas, the common term for various lethal or temporarily disabling gaseous substances used in warfare. The term chemical warfare includes the use of poison gases, as well as incendiary materials and smoke-producing devices.

Lethal poison gases were used in combat primarily in World War I. The first successful use was by the Germans at Ypres in 1915, with results that were disastrous to the French and Canadian troops there. The Allies later adopted gas themselves and retaliated.

World War I showed that gas is useful as a surprise weapon but is not sufficiently decisive, under most circumstances, to be worth the risk of retaliation. Nevertheless, the possibility remains that gas may be used in the future. As a result, many armies maintain branches devoted to the development of gases and defenses against them. Gas masks and heavy, gas-proof clothing protect adequately against most poisonous gases.

Several methods are used to deliver gas in an attack. In the gas cloud, or mist, attack, the wind is used to carry the gas to the enemy lines. Gas can also be delivered in artillery shells and aerial bombs, and can be sprayed from low-flying aircraft.

Types of Gases

The chief types of gases produced for use against humans are blister, choking, nerve, vomiting, and tear gases.

Blister Gases,

such as mustard gas (used in World War I), produce a reddening of the eyes, skin, and mucous membranes, followed by blisters. The bronchial tubes are irritated, and pneumonia usually develops. Mustard gas often remains on the ground for several days. Mustard gas, which is lethal only in heavy concentrations, is used to incapacitate troops.

Choking Gases,

such as chlorine, phosgene, and diphosgene, attack the respiratory tract. Chlorine, first used in World War I, produces quick irritation and choking. The immediate effect of phosgene and diphosgene is less noticeable, but the lungs slowly fill with fluids and the victim suffocates within a few days.

Nerve Gases,

such as Tabun (or GA), Sarin (or GB), and Soman (or GD), are colorless, odorless, and tasteless. These gases destroy the normal functioning of nerves and muscles. The gases enter the body through the lungs, skin, or mucous membranes, and the victim dies within a few minutes after the poisons enter the blood.

Psychochemical Gases,

such as BZ, are incapacitating agents that attack the brain, inducing hallucinations and giddiness in the victims. They are not lethal. BZ was developed by the United States after World War II; its chemical composition has been kept secret.

Vomiting Gases,

such as DM (diphenylaminochloroarsine), rarely kill, but cause severe sneezing, coughing, headache, nausea, and vomiting. DM, also called adamsite, was developed during World War I. Vomiting gases are mainly used in riot control.

Tear Gases,

such as CN (chloroacetophenone) and CS (ochlorobenzalmalononitrile), produce severe eye irritation, resulting in a blinding flow of tears. Tear gases are used principally by police and troops for mob control. CN was first widely used during World War I. CS was developed by the British in the 1950's. In the Vietnamese War, the United States used CN mixed with the vomiting gas DM.