U.S. Air Force Tech. Sgt. Isis Lovette, 633rd Aerospace Medicine Squadron operations noncommissioned officer in charge, prepares Col. James Forrest, 633rd Medical Group vice group commander, for training in the hypobaric chamber at Langley Air Force Base, Va., Dec. 11, 2014. The U.S. Air Force uses hypobaric chambers and Reduced Oxygen Breathing Devices to train Service members how to recognize and endure the symptoms of hypoxia in a life-or-death situation. (U.S. Air Force photo by Airman 1st Class Devin Scott Michaels/Released)