@robryk You can beat the valve as much as you like and at it'll most likely just start leaking propane rapidly (the working pressure doesn't see high enough to make the tank go flying fast, but would require a clean break of the value).

It's only really if the escaping plume meets an ignition source before it disperses that a problem will result (metal against metal action may cause sparks as the valve is being shattered, but it seems that you'd need to be really unlucky for that to happen).

According to this site (https://propanehq.com/how-explosive-is-propane/), the explosive mix between propane and air is approximately 2.1% to 9.5%, so it looks like even if the escaping plume does get lit, that'll most likely end up burning rapidly instead of exploding (although if the tank is overheated to the point that the propane starts boiling and ruptures the tank, the pressure difference is an explosion; https://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion?useskin=monobook but it appears that small tanks don't really have the capacity to allow for the required heating before the contents are exhausted, while large tanks certainly do).