Our high school stacked wood up every year for a huge bonfire for our homecoming game one year we had managed to lash 30 utility poles together in a telescopic fashion the base had 12 40 ft poles Tepee style lashed to a vertical 120ft tree in the center 100s of pickup loads of lumber, pallets and everything else made of wood plus about 100 very old dry bales of hay piled inside and outside all the way to the top of the tree with the remaining poles hauled to the top lashed 1 at a time to the top of the tree hanging down over the stack of rubble, the pile must have been at least 40 feet in diameter but among all of this some "IDIOT" we suspected it was the quarterback had deflated a football then refilled it with a volatile compound and tied it somewhere near the top of the pile The fire was started with several Molotov cocktails thrown at it but no other incendiary fluids that I know of It took several minutes for the fire to rage all the way to the top but that was when everything went south when the football I guess for lack of a better word erupted into a bright blue ball of fire. It wasn't exactly an explosion but close enough it rained flaming particles of debris down and outwards nearly reaching the crowd standing back a couple hundred feet from the base the next year the bonfire was restricted to 40 feet tall