was developed and tested secretly at Porton Down in Wiltshire, UK, in the 1950s and 1960s. CS was used first on animals, and subsequently on British Army servicemen volunteers. CS has less effect on animals because they have different tear ducts and, in the case of non-human mammals, their fur inhibits the free entry of the gas.

As recently as 2002, the U.S. State Department Bureau of International Security and Nonproliferation