ELLSWORTH AIR FORCE BASE, S.D. – Staff Sgt. David Hall, 28th Medical Group bioenvironmental engineering journeyman, conducts a gas mask fit test on Airman 1st Class Anthony Sanchelli, 28th Bomb Wing still photography journeyman, July 7. The fit test will ensure the mask is in good condition and properly fits each Airman. (U.S. Air Force Photo/Airman 1st Class Corey Hook)