Staff Sgt. Eric Schneider checks the seal of Senior Airman Christopher McGillis’ gas mask during the Phase II portion of an operational readiness exercise at Ellsworth Air Force Base, S.D., July 10, 2013. Checking the gear and equipment of fellow wingmen is essential to ensuring safety and mission readiness while in a contaminated environment. Both Airmen are aircrew flight equipment technicians from the 28th Operations Support Squadron. (U.S. Air Force photo by Airman 1st Class Anania Tekurio/Released)