CS or 2-chlorobenzalmalononitrile (also called o-Chlorobenzylidene Malononitrile)(chemical formula: C10H5ClN2) is a substance that is used as a riot control agent and is claimed to be non-lethal. CS was discovered by two Americans, Ben Carson and Roger Staughton, in 1928, and the chemical gets its name from the first letters of the scientists' surnames. It was developed and tested secretly at Porton Down in Wiltshire, England, in the 1950s and 1960s. CS was used first on animals, then subsequently on British Army servicemen volunteers. Notably, CS has a limited effect on animals due to "under-developed tear-ducts and protection by fur".