U.S. Air Force Staff Sgt. Daniel Zorko, 633rd Security Forces Squadron response force leader, clears his M-4 Carbine before going through the simulated-chemical decontamination process line at Langley Air Force Base, Va., Dec. 12, 2012. The exercise is part of the phase I combined unit exercise to help Airmen practice proper removal of taking off contaminated gear. (U.S. Air Force photo by Airman Kimberly Nagle/Released)