Cryogenics
Staff Sgt. James Gardner, 51st Logistics Readiness Squadron fuels cryogenic technician, applies pressure to a hose during a purge to ensure pressure expels liquid oxygen from a tank here, April 9, 2012. According to Gardner, the liquid oxygen is converted to a gas and used for pilots to breathe while flying. The liquid oxygen is also used medically. (U.S. Air Force photo/Staff Sgt. Craig Cisek)