U.S. Navy Chief Petty Officer, Explosive Ordnance Disposal Mobile Unit 12 EOD chief, has his tested a color chart during hypoxia training at 1st Operations Group aerospace and operational physiology, Joint Base Langley-Eustis, Va., Dec. 5, 2017. Towards the end of hypoxia training the instructor turns down the lights and gives the person a card with alternating colors to test their vision while undergoing hypoxia. (U.S. Air Force photo by Airman 1st Class Tristan Biese)