Senior Airman David McMillen, 28th Civil Engineer Squadron heating, ventilation and air conditioning technician, secures water pipes during the installation of a new boiler system in the base Exchange at Ellsworth Air Force Base, S.D., Aug. 15, 2013. The old heating and cooling equipment was replaced with an upgraded environmentally friendly boiler system, which is cost effective and conserves energy. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)