Michael Schmidt, 28th Civil Engineer Squadron heating and air conditioning technician, mounts sheet metal onto a vent to stop airflow during a heating system installation on Ellsworth Air Force Base, S.D., Feb. 2, 2012. The ducts in the room must be completely sealed to prevent the heat from escaping, which helps Ellsworth conserve resources. (U.S. Air Force photo by Airman Alystria Maurer/Released)