U.S. Air Force Airmen wait for an all-clear alert during a Chemical Attack Survival Familiarization exercise at Joint Base Langley- Eustis, Virginia, Feb. 26, 2017. Airmen demonstrated their ability to change into different levels of Mission Oriented Protective Posture gear in the event that they are exposed to a toxic environement. (U.S. Air Force photo by Airman 1st Class Alexandra Singer)