U.S. Air Force Staff Sgt. Richard Weick, 355th Civil Engineer Squadron explosive ordinance disposal, checks the filters on his M50 gas mask during a dismount operations training exercise on Mount Lemmon in the Coronado National Forest, Ariz., Oct. 17, 2013. Weick ensures the filters and the seal on his M50 gas mask are correctly attached so he can breathe properly. (U.S. Air Force photo by Airman 1st Class Josh Slavin/Released)