Airman 1st Class Kyle Dehaan and Jordan Jensen 633rd Security Forces Squadron entry control point guards, check their M-50 gas mask's serial numbers during exercise Coronet White at the Raptor Town entry control point at Langley Air Force Base, Va., April 20. The Airmen received a mock scenario radio message saying that certain gas masks were defective . (U.S. Air Force photo by Senior Airman John D. Strong II/Released)