Firefighter Greg Riley calls for helps during a mock chemical attack as US Navy student Bethjamie Narveaz...
Firefighter Greg Riley calls for helps as United States Navy student Bethjamie Narveaz lies on the concrete porch of the galley during a mock chemical attack at Naval Air Station - Meridian near Meridian, Mississippi, May 5, 2006. The chemical identified as Tabun was the substance used during the attack. According to the Centers for Disease Control and Prevention, tabun is a man-made nerve agent that can be used in chemical warfare. Tabun is also known as "GA" and is colorless, clear and tasteless liquid that can be used as a gas if heated. REUTERS/Kyle Carter