ELLSWORTH AIR FORCE BASE, S.D. -- Airman 1st Class Matthew Hung, 28th Civil Engineer Squadron emergency management journeyman, adjusts his gas mask before participating in an emergency management exercise, June 3. Members from the emergency management section and 28th Medical Group bioenvironmental section combined to perform various scenarios involving chemical, biological, radiological and nuclear detection and decontamination operations. (U.S. Air Force photo/Airman 1st Class Corey Hook)