It depends. If we're talking smokeless powder in 1 lb containers, odds are it won't all ignite in the same couple of milliseconds and generate an aggregated pressure situation. But if we're talking an 8 lb container of smokeless powder the risk goes up exponentially. 8 lbs of powder burning is a tremendous amount of pressure. In open air (outdoors) that's not a big deal (the SAAMI videos show that). In an enclosed space though (like a loading room) that's a problem.
In 2006 the Canadian Explosives Research Lab conducted trials that used to be publicly available (video and report). They did open air trails (no huge issue) and they also ignited an 8 lb container of smokeless powder in a 12' X 12' shed built to National Building Code standards. Basically it generated enough pressure to lift off the roof and a wall fell down. The report indicated that injuries for anyone in the room would be potentially fatal (they had pressure sensors installed).
I've posted this info before and this is where people will chime in saying I'm wrong and there is no danger. Well, whatever... I'm not sending my firefighters into a fire where I know 8 lb containers of smokeless powder are threatened (or 1 lb containers of black powder for that matter). Loaded cartridges of sporting ammo, no problem. Last fire like that we had, the guy had an entire pallet of shotgun shells in his garage for the trap season. We saved the house.