U.S. Air Force Senior Airman Ronell Tennant, 633rd Civil Engineer Squadron emergency management technician, tightens his breathing apparatus during a training exercise at Langley Air Force Base, Va., May 16, 2013. The training included personnel from the 633rd Medical Group’s bioenvironmental division and the 633rd CES’s fire and emergency services. (U.S. Air Force photo by Airman 1st Class Austin Harvill/Released)