A U.S. Air Force Airman from the 455th Expeditionary Logistics Readiness Squadron refills liquid oxygen carts at Bagram Airfield, Afghanistan Sept. 5, 2014. Cryogenic technicians work with extremely cold substances that boil at subzero temperatures then evaporate into breathable air. The cryogenics technicians support 6,000 aircraft missions and issue more than 4,000 gallons of liquid oxygen per month.
U.S. Air Force photo by Staff Sgt. Evelyn Chavez/Released
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