South Korean and U.S. Marines break the seal of their gas masks during the Korean Marine Exchange Program 15-17 on the Cham Sae Mi Close-Quarters Battle Training Facility in Pohang, South Korea, Feb. 9, 2015. Breaking the seal allows the Marines to be exposed to the chemical agent in the air. South Korean and U.S. Marines break the seal of their gas masks during the Korean Marine Exchange Program 15-17 on the Cham Sae Mi Close-Quarters Battle Training Facility in Pohang, South Korea, Feb. 9, 2015. Breaking the seal allows the Marines to be exposed to the chemical agent in the air. SHARE: Download: Full Size (0.54 MB) Tags: photo essays Credit: VIRIN: 625870-P-ZHH92-398.jpg Photo Gallery