U.S. Marine Corps Cpl. Thomas Ellensohn, a cyber systems administrator with 6th Communication Battalion, Force Headquarters Group, shakes his gas mask during gas chamber training at Marine Corps Base Camp Lejeune, North Carolina, Oct. 22, 2019. The DPC/RSU-East staff conducted gas chamber training, an annual training event, requiring Marines to be exposed to chlorobenzalmalononitrile tablets, also known as CS gas, in order to familiarize themselves with their gas mask. (U.S. Marine Corps photo by Sgt. Andy O. Martinez)