What's the chances...

[heat checker]

Of a 20lb LP tank exploding? Today, while icefishing, a couple guys came over and wanting advice. They had lit there "sunflower" type heater and had a fire "not where its supposed to be". I'm geussing the pipe going up to burner was plugged causing gas to come out by plastic adj knob, which caught on fire. Had about a foot of flame until plastic knob burned and fell off. First instinct was to run up and turn main valve off on tank, but the thought of it exploding came to mind and we backed off. Ended up dieing out by itself. Tank was not even warm when I shut the valve off. What IS the chance that they can explode or send out large flame capable of causing injury?

[Sandmannd]

I don't know what the chances are, but I think you did the right thing. Maybe throw some snow from a ways away at it. But always gotta bear carful of flames and gas.

[Surface Tension]

You would have been safe to close the valve off. Its going to take a very long time in direct heat and then the first thing to happen is propane will start bleeding out the pressure relief valve. That pressure relief valve is there to prevent the tank from rupturing.

Anyway, propane will start to pass through the valve slowly, as the heat increases so will the pressure inside that tank. That is why your not supposed to have a tank inside a building or fish house. If that pressure relief valve lets out propane with a sunflower attached it will ignite. Worse yet propane leaking out a PRV inside your home or garage, you turn the light on and BOOM.