Senior Airman David McMillen, 28th Civil Engineer Squadron heating, ventilation and air conditioning technician, connects 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 28th CES HVAC Airmen maintain, install and repair refrigeration, ventalation and heating systems, saving the Air Force more than $75,000 per job. (U.S. Air Force photo by Airman 1st Class Zachary Hada/Released)