U.S. Air Force Senior Airman Francia Bienvue, 633rd Aerospace Medicine Squadron physiology technician, dons her mask before going through a rapid decompression test with high-altitude training students in a hypobaric altitude chamber at Langley Air Force Base, Va., Nov. 14, 2014. Students go through a series of tests that bring on hypoxia and add pressure to sinus cavities. (U.S. Air Force photo by Staff Sgt. Natasha Stannard/Released)