I’ve often wondered how most guys store powder safely. Mine is pretty much in closets but I know it’s certainly not the best. I really don’t have a detached structure to store it, and worried about the extreme temperatures of my attached garage. No good way I suppose without it being removed from the house.
Cool and dry, and in a non contained structure.
Just take a look at how retail stores store and display powders. Do you think their insurance policies and or local fire codes don't have a say in how it's stored or displayed?
Climate controlled, open shelving, or boxes that won't contain pressure. A locked steel cabinet is the worst possible way.