U.S. Air Force Senior Airman Francia Holt, an aerospace and operational physiology technician assigned to 633rd Aerospace Medicine Squadron, adjusts the straps on a Reduced Oxygen Breathing Device at Langley Air Force Base, Va., April 19, 2016. Aerospace physiologists ensure aircrew members understand the potential threats oxygen deprivation and depressurization have on the body. (U.S. Air Force photo by Airman 1st Class Kaylee Dubois)