Jerry Riley, Headquarters Air Force Civil Engineer Support Agency heating, venting and air conditioning equipment specialist, controls a backpressure compensated air balance system in Building 7450 during an inspection at Ellsworth Air Force Base, S.D., Sept. 19, 2012. The system automatically calculates airflow data and converts these readings to local density results, which allows for more healthy and energy efficient facilities at Ellsworth. (U.S. Air Force photo by Airman 1st Class Kate Thornton-Maurer/Released)