U.S. Marine Corps Cpl. Jigme Tsering, a network administrator with 6th Communication Battalion, Force Headquarters Group, breaks the seal of his gas mask during gas chamber training at Marine Corps Base Camp Lejeune, North Carolina, Oct. 22, 2019. The DPC/RSU-East staff provide activated Reserve units/dets various types of training such as gas chamber qualification. During the qualification, Marines are taught chemical, biological, radiological and nuclear threats, reactions to CBRN attacks, and how to take proper care and use of a gas mask. (U.S. Marine Corps photo by Sgt. Andy O. Martinez)