Soldiers of Headquarters and Headquarters Company, 1st Stryker Brigade Combat Team, 4th Infantry Division, expose themselves to o-Chlorobenzylidene Malononitrile (tear gas) inside the range 72 gas chamber by removing their M40-series protective masks during annual chemical, biological, radiological and nuclear training, Jan. 8, 2015. The "CS" gas was discovered by Americans Ben Corson and Roger Staughton in 1928 and the chemical gets its name from the first letters of the scientists' surnames.