Staff Sgt. Kathleen Couillard, 28th Medical Operations Squadron bio-environmental engineering technician, starts an x-ray machine during a radiation scatter survey at the dental clinic on Ellsworth Air Force Base, S.D., March 27, 2012. Once the x-ray machine starts emitting radiation, the ion chamber survey meters will pick up a reading to provide an accurate measurement of radiation levels present within the facility. (U.S. Air Force photo by Airman 1st Class Kate Thornton/Released)