Participants in the Air Force Research Laboratory's 2015 Tech Warrior exercise leave a tunnel after the release of a smoke grenade simulating mustard gas during a training scenario at the National Center for Medical Readiness in Fairborn, Ohio, Sept. 15, 2015. During the exercise, participants learned a variety of skills such as base defense, self-aid and buddy care, and tactical vehicle driving and land navigation. U.S. Air Force photo by Wesley Farnsworth