U.S. Air Force Staff Sgt. Nicholas Flamm, a 509th Logistics Readiness Squadron fuels service center operator, utilizes a refractometer to measure fuel system icing inhibitor (FSII) levels at Whiteman Air Force Base, Mo., Nov. 3, 2015. This process ensures the FSII levels meet the Air Force specifications and keeps ice crystals from forming in the fuel during flight. (U.S. Air Force photo by Senior Airman Keenan Berry)