Senior Airman Derek Hunter checks electrical circuits on a heating ventilation and cooling system April 21,2011, at Kadena Air Base, Japan. Kadena AB officials recently instituted an initiative through the Air Force Smart Operations for the 21st Century program to replace the antiquated outdoor AC chillers with protected indoor equipment to potentially save the Air Force millions of dollars in parts and energy. Hunter is an 18th Civil Engineer Squadron HVAC and refrigeration technician. (U.S. Air Force photo/Staff Sgt. Jonathan Steffen)