100LL and the fumes from 100LL are highly flammable (much like Tracefi's posts). I can see, the fumes especially, coming in contact with flames being very devastating in an explosive way.
Some jet fuels on the other hand, not so much. I have heard of people dropping lit cagarettes into a tank of jet fuel without setting it off (it was done as a demonstration).
I've seen that same demonstration. Its the fumes that burn, the liquid in close proximity to the heat vaporizes and burns. It has to do with the condition (temp, pressure, and vapor pressure) of the liquid.
the whole group of veteran oilfield trash observing this demonstration ducked, turned, and unassed the area. Even after the explanation of why it wouldnt catch fire.
Stab