CN gas

Not to be confused with hydrogen cyanide, HCN.

CN, or chloroacetophenone, is a substance used as a riot control agent. It has the molecular formula C₈H₇ClO. It was investigated, but not used, during the First and Second World Wars, and was used by United States forces in Vietnam. Because of its greater toxicity, it has largely been supplanted by CS gas.

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CN is still supplied to paramilitary and police forces in a small pressurized aerosol can known as “Mace” or tear gas. Its use has fallen by the wayside as pepper spray works faster and disperses more quickly than CN.

The term "Mace" came into being because it was the brand-name invented by one of the first American manufacturers of CN aerosol sprays. Subsequently, Mace became synonymous with tear-gas sprays in the same way that Hoover has became strongly associated with vacuum cleaners.

Like CS gas, this compound irritates the mucous membranes (oral, nasal, conjunctival and tracheobronchial). Sometimes it can give rise to more generalized reactions such as syncope, temporary loss of balance and orientation. More rarely, cutaneous irritating outbreaks have been observed and allergic contact permanent dermatitis.