CR gas or dibenzoxazepine (also referred to as DBO), or its chemical name dibenz[b,f][1,4]oxazepine, is an incapacitating agent and a lachrymatory agent. CR was developed by the British Ministry of Defence as a riot control agent in the late 1950s and early 1960s. A report from the Porton Down laboratories described exposure as 'like being thrown blindfolded into a bed of stinging nettles', and it earned the nickname "firegas".