U.S. Marine Corps Gunnery Sgt. A. I. Thomas, 5th Marine Regiment Chemical, Biological, Radioactive, Nuclear (CBRN) Chief, gives a class on how to use the M256 Vapor kit to check for contaminants during a CBRN drill as a part of Exercise STEEL KNIGHT 2014 aboard Marine Corps Air Ground Combat Center Twentynine Palms, Calif., Dec. 14, 2013. Steel Knight enables 1st Marine Division to test and refine its command and control capabilities by acting as the headquarters element for a forward-deployed Marine Expeditionary force. (U.S. Marine Corps photo by Cpl. Justin A. Bopp, 1st Marine Division Combat Camera / Released)