Antony Dapiran in Ninth Letter:
Tear gas rounds describe a graceful arc as they drop down out of the blue sky, trailing feathery tails of smoke like streamers. The shells hit the road with a ping, and sparks fly as they skip gaily along the asphalt. As they roll to a stop, the shells hiss like an angry snake, dense smoke pouring out of the top of the small aluminum canister, and soon the street is enveloped in clouds.
The most important thing to understand about tear gas is that it is not a gas. It is a substance, a sort of powder, delivered in the form of smoke from a burning tear gas shell. That powder is 2-chlorobenzylidene malononitrile, known as “CS”—a compound developed and tested at the United Kingdom’s notorious Porton Down military facility. As the tear gas canister burns, which it does for around a minute, it spreads smoke containing tiny particles of CS that stick: to clothes, to skin, to surfaces.
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