Airman 1st Class Zane Zeitler and Staff Sgt. Jose Hinojosa, 28th Civil Engineer Squadron heating, ventilation and air conditioning repair technicians, analyze combustion efficiency levels on a HydroTherm Boiler at Ellsworth Air Force Base, S.D., Oct. 8, 2014. The HydroTherm boiler is one of 70 boilers that have been installed in facilities throughout the base that modulates water temperatures in relation to outdoor weather temperatures reducing energy output by more than 20 percent. (U.S. Air Force photo by Senior Airman Anania Tekurio/Released)