Tear Gas

I

Introduction

Tear Gas, chemical substance that produces a primary physical effect of stinging or tearing eyes. Tear gas also irritates other mucous membranes and causes choking and coughing. People exposed to higher concentrations may experience burning, itching, or even blistering skin. As a form of riot control, police often use clouds of tear gas to break up crowds of people. A rifle-fired grenade or a thrown canister usually delivers tear gas, but smaller hand-held spray devices also exist. Tear gas may also be used to force the surrender of fugitives hiding in a building. Dogs and horses are relatively unaffected by tear gas, so they can add to the riot-control effect of the gas.

II

Types of Tear Gas

CN and CS are the two main types of tear gas. CN’s scientific name is chloroacetophenone, and it comes in several variants. CNB adds benzene and carbon tetrachloride, while CNC adds chloroform. CNS adds chloropicrin (PS), which can cause victims to vomit or suffer lung damage. CN was discovered in Germany in the 1860s. It was used early in World War I (1914-1918) with mixed results.

CS’s scientific name is chlorobenzylidene malononitrile. It was first made in the 1920s. It is considered less toxic and more potent than CN and is used much more often. A person engulfed by CS begins tearing, coughing, and feeling dizzy or nauseous. Unlike CN, CS can be washed off easily.

III

History

Tear gas was first used early in World War I, setting the stage for the use of stronger chemical warfare agents like chlorine in 1915. Compared to the effects of these chemical agents, the effects of tear gas are milder and shorter-lived, so that tear gas was deemed an ineffective weapon against prepared troops. However, tear gas was used during the Vietnam War (1959-1975) by United States troops to aid in combat operations.

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After World War I, police and internal security forces became the largest users of tear gas, using it mainly as a riot-control agent. Some notable events that saw extensive use of tear gas include the Bonus March in Washington, D.C., in 1932, the Democratic Party’s Chicago Convention of 1968, frequent Israeli-Palestinian clashes, and the siege of the Branch Davidian compound near Waco, Texas, in 1993.

Current police training suggests using CN in confined spaces and CS outdoors. Critics of tear-gas use say that because the concentrations cannot be controlled, dense pockets of gas may cause death or injury. Also, the projectiles carrying the gas can injure and even kill. Very little is known about long-term side effects, although research suggests that the risk is low. Some forms of tear gas are available for personal protection.

See also Chemical and Biological Warfare.

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