Double-chamber cob oven

https://www.youtube.com/watch?v=TvrUrnEIQoo

http://www.scubbly.com/item/75815/

A normal cob oven is a structure with one chamber for fire and for cooking. This has been improved upon with the technology of rocket stoves and using the double burn principle. Normal cob ovens lose energy from the exhaust of the fire. When a second chamber and flu are added, the smoke from the initial burn, burns and the exhaust is nearly clear. The only downside I see to this is the double chamber oven needs to be covered in the wet season because adding a roof structure would not work with the design. It might be possible to make the exhaust pipe longer thus enabling the construction of a roof but that would require further research.