The View From North Central Idaho

But how would they ignite it? You need an initial gunpowder charge to set it off, which the dogs can sniff out, plus the TSA will be able to detect the liquid. Nice explosions though.

a fine powder of almost anything, [sufficiently] dispersed in the presence of oxygen/air (ie, "free" oxygen not already in a molecule with something else, as it is in water) will burn, often rapidly enough to qualify as an explosion. Actually, I am surprised noone has yet posted about grain elevators or flour mills.

They actually did a Mythbusters episode of this. The episode was focusing on some viral videos, one of which was someone doing this with sawdust. After they got the smaller sawdust fireball, they went for a much bigger one with non-dairy creamer.

for both, they just stuck a flare in the top of the powder and then set off the explosion by pumping a large quantity of compressed air into the drum from the bottom. Episodes like that make me extremely jealous of those guys. It's one thing to play around with things like that. It's another to actually be paid for it. The fact that I can't think of a single place within a couple hundred miles of me that I could do that safely doesn't help matters either.

OrangeNeckInNY, I've only given it a few seconds of thought but what first comes to mind is a balloon that is popped when a match is lit. The balloon disperses the powder and the match ignites the fuel air mixture. Even ground up match heads could probably be used as an adequate substitute for the gunpowder. Or the balloon could be filled with a mixture of propane and oxygen. The ideas are come out of my head faster than I can type...

Fuel, meet air. You two are going to get along just great. Oh look, here's my friend ignition source...

I know I said it before... but COOOOOOOOOL....... fireballs!