U.S. Marines with Headquarters and Service Battalion,

U.S. Marines with Headquarters and Service Battalion, and Weapons Field and Training Battalion, Marine Corps Recruit Depot Parris Island, line up outside the gas chamber during an individual protective equipment confidence exercise, also known as the gas chamber, aboard Marine Corps Recruit Depot Parris Island, S.C., March 21, 2012. The gas chamber is implemented to teach Marines how to avoid panic in the chance that they may have to serve in a contaminated environment.