A soldier breaks the seal to an M40 field protective mask during chemical, biological, radiological and nuclear sustainment training on Joint Base Elmendorf-Richardson, Alaska, July 16, 2015. A soldier breaks the seal to an M40 field protective mask during chemical, biological, radiological and nuclear sustainment training on Joint Base Elmendorf-Richardson, Alaska, July 16, 2015. SHARE: Download: Full Size (2.450967 MB) Tags: Photo Essays Credit: VIRIN: 602473-F-NUA70-955.jpg Photo Gallery