YOKOTA AIR BASE, Japan -- Airman 1st Class Jacob Trout, a 374th Civil Engineer Squadron heating, ventilation and air conditioning technician, checks the flow of underground heating valves before operating the system Oct. 14, 2010 at Yokota Air Base, Japan. The HVAC shop maintains the heating and cooling systems for over 1,000 facilities. (U.S. Air Force photo/Osakabe Yasuo)