Staff Sgt. Dallas English, 28th Logistics Readiness Squadron fuels laboratory NCO in charge, looks into a refractometer during a test inside the fuels lab at Ellsworth Air Force Base, S.D, March 26, 2013. The refractometer is used to test icing inhibitor content levels in the fuel system, which lowers the freezing point of water and allows normal operations in cold temperatures. (U.S. Air Force photo by Airman 1st Class Anania Tekurio/Released)