Laukton Rimpel, a field training instructor from the U.S. Army Medical Research Institute of Chemical Defense, explains how to wear a M50 gas mask during PATRIOT North 18 at Volk Field, Wis., July 16, 2018. PATRIOT is a Domestic Operations disaster-response training exercise conducted by National Guard units working with federal, state and local emergency management agencies and first responders. (U.S. Air National Guard photo by Senior Airman Julia Santiago)