U.S. Air Force Capt. Max Alvarado, 633rd Aerospace Medical Squadron aerospace physiologist, adjusts the Reduced Oxygen Breathing Device during a training session at Langley Air Force Base, Va., June 25, 2014. The ROBD can be used in place of the altitude chamber for hypoxia awareness retraining, although it doesn’t simulate the other effects of high-altitude operations. (U.S. Air Force photo by Senior Airman Austin Harvill/Released)