Airman 1st Class Kelsey Chavez, 47th Operations Support Squadron aircrew fabrication equipment technician, cleans an oxygen tube from an oxygen mask at Laughlin Air Force Base, Texas, June 19, 2013. The masks are used in conjunction with an on-board oxygen generating system to create oxygen based on the pilot’s altitude during a flight. (U.S. Air Force photo/Airman 1st Class John D. Partlow)