Tech Sgt. Ben Reid, 433rd Aircraft Maintenance Squadron crew chief, dons his gas mask during an Ability to Survive and Operate training exercise along the flight line on Joint Base San Antonio-Lackland, Texas on Nov. 18, 2017. The focus of the training was geared toward responding to chemical, biological, radiological and nuclear threats in a deployed environment. (U.S. Air Force photo/Senior Airman Bryan Swink)