I've seen one in action. It burns hot even at start up and isn't sooty. The stove is an updraft gasifier that uses air instead of an inert gas. The combustion is very clean as an excess of oxygen is forced over the wood and that burns the fuel completely. The stove was very loud, however. The internal fan that makes the "updraft" is always running. There is also no temperature control on it. It burns at one temperature...hot!