LANGLEY AIR FORCE BASE, Va. -- Staff Sgt. Joseph Dunn and Senior Airman Ryan Gross, 633d Civil Engineer Squadron Fire Department firefighters, escort Airmen with mock burns away from the scene of a simulated explosion during a Major Accident Response Exercise Feb. 4. MAREs are held on a semi-annual basis to certify and train base emergency responders. (U.S. Air Force photo / Senior Airman Wesley Farnsworth) (RELEASED)