I begin to wonder about people these days, based on comments like this. Have none of you ever seen or heard of a " bung"? That is the wooden plug that is put into the wooden barrel in which beer and some wines are placed. It acts as a pressure release valve should the pressure inside the cask builds up too much.
The same thing can be done with any metal container used to store powder. If you bury the container at, or below ground level, any explosion will be directed upward, where it poses very little harm to man or property. ( That is why you carry your rifle with the muzzle pointed up, around people, no?) Powder stored in the metal cans that its sold in pose no particular danger of exploding, since the soldered seam is the " pressure release system " designed into the can. If you put an insulated cover over the storage container, whatever its made from, the container is not going to get hot enough to ignite the powder in the cans below. HEAT RISES! That means it rises above the ground, too. Use a wood pallet, but fill it with styrofoam for better insulation, and then put a thin metal cover on top of the pallet, to cover your powder container in the ground. YOu can stack " stuff " on it to deter anyone from digging down to it, for security. Let the metal plate get rusty. That will really deter others from thinking there is anything under it of value, as they won't want to get their hands dirty lifting it. If someone tries, and finds it screwed to something heavier underneath, they will give up.
If you drill a large hole(s) in the top of the container, and then plug it with a wooden plug( or cork), you have your safety valve to let gases escape upward, and safely, rather than sideways where they might ignite more powder. Do put some baffles in the storage box. Any wood will serve as an insulator from heat, and delay the spread of any fire. There are fire proofing compounds that can be " painted " on the wood baffles to supply even more protection. Finally, there is a foam spray now available to can be strayed to the inside and underside of you cover, both the interior and the exterior, which melts into water when heated hot enough, and that can also prevent the powder from igniting. The evaporation of the water tends to cool fire, and also cools down whatever the water is on.
If the firefighters won't water down your powder magazine, use a garden hose, or bucket of water to water it down. If its outside your house, you should be able to get to it even if your house is burning. A friend of mine put a small storage shed, where he keeps his lawn mower, and garden tools on top of his " powder magazine". The shed is held to the ground with long screws, similar to the kind of thing sold for tying a dog leash to. Short of a tornado, the shed is not moving. It gets very hot in the shed in summers, but his magazine stays cool below. He parks the lawn mower on the metal cover, so it looks like that is why the cover is on the ground inside the shed in the first place. Give a crook a rational explanation for why something is in a particular place, and he rarely is going to look further. My friend has a lock, of course, on the shed. And there is another lock on the lid of the powder magazine.
