This idea of an explosion spreading poison gas around is reminiscent of an event in the first invasion of Iraq (the senior George Bush was president at that time).  At that time, Iraq did have stock piles of poison gas which the Iraq military had used in their war against Iran.  The U.S. destroyed Iraq's stockpiles, but they did it in a rather unusual way.  They blew up the munitions dump where the poison gas was stored, sending a plume of toxic material up into the air, which drifted over a large area. Yes the explosion did destroy much of the poison gas, but so much was stored, that the rest of the material went up into the air.