2-chlorobenzalmalononitrile (chemical formula: C10H5ClN2) is a substance that is used as a riot control agent and is usually claimed to be non-lethal by the forces who use it. CS was discovered by two Americans, Ben Carson and Roger Staughton in 1928, the first letters of the scientists' surname giving us the name of the substance, 'CS' . It was developed and tested secretly at Porton Down in Wiltshire, England. Apparently this testing occurred in the 1950s and 1960s when CS was used firstly 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. . (from Wikipedia). Known as tear or pepper gas, often used by paramilitary and police to control unruly crowds, the gas can cause temporary blindness and tearing.