Staff Sergeants Kyle Martin and Jason Leavens, 811th Security Forces Squadron executive aircraft security members ran with gas masks during the 11th Security Forces Group National Police Week Ruck March on May 15, 2013 at Joint Base Andrews, Md. The gas masks can make it harder to breathe, due to reduced air flow through the filter. (U.S. Air Force photo/Airman 1st Class Nesha Humes)