U.S. Air Force Airmen walk through a simulated attack scene during an Ability to Survive and Operate (ATSO) exercise at Rosecrans Air National Guard Base, Mo., Apr. 4, 2014. The ATSO exercise gave Airmen the opportunity to practice how to correctly don their protective uniform, describe an attack scene to authorities, and move from a contaminated zone to a clean zone. (U.S. Air National Guard photo by Tech. Sgt. Theo Ramsey/Released)