Marines with Combat Logistics Regiment 27, 2nd Marine Logistics Group, give the gas chamber instructor a thumbs-up, confirming the functionality of their gas masks, during a gas chamber training exercise aboard Camp Lejeune, N.C., Feb. 19, 2010. The gas chamber is an annual requirement for all Marines in order to build confidence in their gear and ensure it functions properly. (U.S. Marine Corps photo by Lance Cpl. Melissa A. Latty)

Photo by Lance Cpl. Melissa A. Latty