This is a large stage version of a fire tornado that is designed to impress in a large venue. It is about 2.8m high and the spinning column of flame can come out another metre above that (Make sure the ceiling is high enough!).
It is made of welded aluminium and steel with a large base for stability, and the two halves of the tube slide inside one another for transport.
Hot air from the flames rises because cold air is coming in from the side causing the hot air to float up. The cold air is spinning slowly so when it moves inwards it spins faster and faster due to the conservation of angular momentum. This high wind picks up fuel, and the centrifugal force makes it hard for oxygen to get to the flame, so it burns slow and sooty, in a beautiful spinning flame.