A propane refill class was just held about 15 yards from where I'm typing,
I do not know the explosive power of Propane off hand but I do know it is serious. however for the maximum effect, be it propane, Natural gas or gasoline vapor, you need the proper mixture of Air and Fuel.. once that happens, add an ignition source, A spark from a switch opening or closing, a cigarette ash, a lighter, two pieces of metal striking each other, a hot wire.
And.... Well, when the instructor ask what happens.. I answered "you land one county over" he liked my answer (The proper answer was an explosion but I put it better).
That said.. I have lived with propane many many years, Grew up with it in fact, and never in 59 years of living with propane (I'm 62 by the way) and natural gas as well, have I had a problem. Came close one time... but replaced the defective device before the problem manifested. (Discovered the problem while loading it on the scrap truck that hauled it away via visual inspection.. the best way to find one I might add)