Crew chiefs assigned to the 2nd Aircraft Maintenance Squadron, put on respirators prior to the "cart-start" of a B-52H Stratofortress, Sept. 18, 2014, Barksdale Air Force Base, La. Impulse carts are installed in the engines, giving them a jumpstart on ignition, which lessens the engine start time, but produces a large plume of smoke. (U.S. Air Force photo by Master Sgt. Greg Steele/Released)