Well, it depends. As long as you can add enough co2 to overcome the loss to venting, it can still work.
But as noted, if you burn a yellow flame, you will produce co. The flame needs to be blue/clear. No yellow.
A co alarm would also be recommended.
But with all the gear washing up on ebay, I wouldn't bother building one. Just find a cheap 4 burner setup, close off two of the burners, and put a controller on it.
Or use bottled co2.