to see some really big flame cannons have a look on mtfx site. i used to work for them and watched the testing of the big flame cannon. 25 kgs of propane helped by a big tank of co2 to get the pressure up to 300psi or there abouts. you light the pilot release some propane light it then open the co2 valve. 25 kgs of propane gone in 2 seconds. the flame is about 60 foot high. just the thing for a party, if somewhat expensive in gas. need i say don't try this indoors.
