Heating, ventilation, air conditioning, and refrigeration Airmen maintain heating and cooling on base
Senior Airman Kristian Martinez-felix, left, a 319th Civil Engineer Squadron heating, ventilation, air conditioning and refrigeration apprentice, and Senior Airman Tristan Miles, a 319th HVAC-R journeyman, maintain the water boilers June 20, 2018, on Grand Forks Air Force Base, North Dakota. Martinez-felix said that they typically work on the water boilers in the summertime to ensure they are prepared for the winter months. (U.S. Air Force photo by Airman 1st Class Melody Wolff)