Tear Gas: Okay for Protests but Banned in War!

The term “tear-gas” covers a range of chemicals, of which the most widely used include o-chlorobensylidene malononitrile (cs), oleoresin capsicum (oc, or pepper spray) and 1-chloroacetophenone (cn).

The gases are in fact powders, and new variants are designed to disperse slowly.

Bizarrely, chemicals that are so often used on civilians are banned for military use.

Tear-gas was first used in battle during the first world war. The use of such gases in that conflict led to their outlawing under the Geneva Protocol of 1925.

Armies skirted the ban at times, for example, the US used CS gas in Vietnam.

But the ban on military use was also part of the Chemical Weapons Convention of 1993.

After the first world war, tear-gas became a popular “riot-control agent” in the US and the British empire. Regarding the unrest in Hong Kong, police are following procedures devised by British colonial administrators.

The War Office required a “declared intention to use tear-gas and adequate warnings” be given to opponents. The obfuscatory term “smoke” was promoted.

In the words of Henry Duffield Craik, a governor of Punjab under the British Raj from 1938 to 1941, “Gas is a much more alarming term, as it suggests something resembling the poison gas used by the Germans in the last war.”

Although the short-term effects of tear-gas are unpleasant, they diminish quickly, but little is known about the long-term impact (clinical trials are impossible). However, the dangers come more from its misuse than from the gas itself.

There are guidelines or conditions which must be met:

  • That there is a way for a crowd to disperse;
  • That the area is well ventilated; and
  • That the gas is fired into the ground in front of protesters, not in the air or at their heads – especially when the canisters are large and may be lethal.

Military police squads, rescue teams, and special forces will use a respirator or military-grade gas mask to protect themselves from a wide range of gases and chemical agents that civilians also now use against tear gas during protests.


The Economist. (2019) Tear-Gas: A Crying Game. The Economist. 16 November 2019, pp.56.


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