200114-Z-NJ935-0229
U.S. Air Force Master Sgt. Eric Harris, a 173rd Fighter Wing crew chief, refills the oxygen bottle aboard an F-15 using a portable liquid oxygen system, during travel to the 162nd Fighter Wing in Tucson, Ariz., Jan. 14, 2020. Liquid Oxygen is a cryogenic liquid with a temperature lower than negative 130-degrees, making skin contact dangerous due to freezing burns, hence the heavy protective gear. (U.S. Air National Guard photo by Master Sgt. Jefferson Thompson)