[dayman]

Without a barrel around it to contain and direct the discharge there isn't enough powder in a cartridge to cause any major issues. There was actually a myth-busters episode that covered it.
You wouldn't want to be right next to it, but if your house is burning so hot that your ammo starts popping while you're in the room some minor lacerations are going to be the least of your worries.

I keep mine in a footlocker