[gas0linealley]

"In an explosion there has to be a fuel that explosively combusts."

Not so. Boiler explosions are just one example.

[Blueflag]

I was speaking technically, as a firefighter (past life). The rupture of a presssure vessel, like a "boiler explosion" indeed has all the effects of an 'explosion', it's just TECHNICALLY explosive decompression, not an 'explosion.' But I admit that's being pedantic. Just so ya know, dictionary.com agrees with you, not me ;-) ex·plo·sion /ɪkˈsploʊʒən/ Pronunciation Key - Show Spelled Pronunciation[ik-sploh-zhuhn] Pronunciation Key - Show IPA Pronunciation –noun 1. an act or instance of exploding; a violent expansion or bursting with noise, as of gunpowder or a boiler (opposed to implosion).