U.S. Air Force maintenance personnel with the 169th

U.S. Air Force maintenance personnel with the 169th Fighter Wing at McEntire Joint National Guard Base, S.C., don their gas masks in response to a simulated chemical attack on the flight line during a Phase II Readiness Exercise, April 12, 2013. Members of the 169th Fighter Wing are preparing for a Phase I and II Readiness Inspection, which evaluates a unit’s ability to deploy, then operate and launch missions in a chemical combat environment. (U.S. Air National Guard photo by Tech. Sgt. Caycee Watson/Released)