text: about 250 pounds of an ammonia-based chemical exploded into a large fireball and gas cloud about 11 a.m. monda ...blowing the roof off of a plant that makes devices for military aircraft ejection seats, fire officials said.  william hermann and ginger richardson the arizona republic mar. 14, 2006 12:00 am  could it be sodium azide?  isn't "ammonia based" pretty non-specific? ammonia perchlorate.