ELLSWORTH AIR FORCE BASE S.D. - Airman 1st Class David Jack, 28th Civil Engineer Squadron emergency management journeyman, is fitted in a level A suit before participating in an emergency management exercise, June 3. In real world incidents, level A suits are donned when emergency responders deal with an unknown variable in a chemical, biological, radiological and nuclear environment. (U.S. Air Force photo/Airman 1st Class Corey Hook)