U.S. Air Force Airmen 1st Class Aaron Ohlemacher and Jedadiah Floyd, 31st Civil Engineer Squadron heating, ventilation, air conditioning and refrigeration technician, cleans an air filter, July 29, 2015, at Aviano Air Base, Italy. HVAC Technicians clean air filters every quarter, ensuring all machine parts are properly working. (U.S. Air Force photo by Airman 1st Class Deana Heitzman/Released)

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