The air enters the outer canister holes in the bottom and feeds oxygen through the holes in the base and bottom of sides of the inner cannister. Heated air travels up between the canisters and exits the holes in the top of the inner canister. You can see in the first image of my test stove, that the flames actually exit the inner top holes. Virtually smoke free.
As far as it being "open vestiblule" im not sure what you mean by that. But, to make it trail safe, you could place a piece of expanded metal (like what is inside at the bottom) on top, under the pot stand. That would make it an enclosed fire. Here in Manitoba, when the fire ban is on, this would make it compliant.
Heres a diagram of how the design works:


And FYI, the tester I made was a small coffee tin and a chunky soup can inside. only a few ounces in weight.


Edited by BTTB (06/26/14 05:51 PM)