I assume HBAR's explanation was satisfactory. I have worked 4 safe explosion cases, 2 were powder ignition, one from an electric dehumidifier and one undetermined. The other two were ammunition cooking off. One was a robbery gone bad with a torch causing the ignition and the other was a house fire in the mountains.

On a few of the grounders, ammo in the safe had cooked off, but the quantity was low. Lots of damage to the interior and the guns, but no explosion of the safe itself.