Staff Sgt. Shaun Ouellette, 11th Civil Engineer Squadron readiness and emergency manager, tightens a bolt on an oxygen tank seal during a hazardous material training scenario on Joint Base Andrews, Md., Sept. 29, 2016. 11th CES prioritizes exercises so they are equipped to react to any HAZMAT leakage or spill. The objective of the simulations was to control and stop a leak, which was achieved by tightening bolts, hammering plugs and patching cracks. (U.S. Air Force photo by Airman 1st Class Valentina Lopez)