I feel obligated to explain the scheme of the Maximus oven which was previously posted in this thread, and its relationship to heat.
Please see below schematics of Maximus and a typical EPA wood heat stove. As many of you may know EPA was introduced to provide more efficient technology into wood burning - cleaner, more efficient, hotter. A crucial component of an EPA stove - the piece that larger makes all of these advances possible if the Baffle. The purpose of the baffle is to make the smoke path longer. A little known fact is that wood smoke can be burnt, just like any other fuel, and it will provide heat. However, it can only be burnt at very high temperatures. If smoke goes right into the chimney from the fire chamber it doesn't have enough time to heat to the smoke burning temperature and hence hot unburnt gases escape into the air. This means: air pollution and heat loss / inefficient heating. The way to make wood smoke burnt is to keep it inside the oven for longer time + provide it with some fresh combustion oxygen / air. This is where the baffle comes into place - it stands in the way of the smoke and sends it twice along the entire depth of the oven before the smoke is allowed to escape. The smoke heats up and gets reburnt inside the oven. A good EPA smoke will emit little less than vapor out of it's chimney - relatively cold and almost completely devoid of unburnt gases.
This is how the Maximus oven was built. It's the only oven i'm aware of which employs the EPA system to provide hotter and more efficient heat. As the hot smoke travels under the baffle from the back of the oven into the front it encounters fresh air from the door opening of the oven and get reburnt. The result is that you have fire even inside the chimney of the oven - over the baffle! And hence cleaner air, hotter inside, less wood to use. Hope this clarifies the oven's construction.