Making a retort

I finally have all of the pieces needed to make a retort style biochar creator (YAY).  There's one part in all of the videos I've watched, and posts I've read, that I need clarification on.

The inner barrel is enclosed on the top and holes are put in the bottom to allow the gasses to exit and burn off.  Since hot air/gasses rise I would think it would be more effective to put the holes into the top of the inner barrel.

Could somebody help me understand why the holes are put into the bottom instead of the top of the inner barrel?

The holes are put on the bottom because as the wood inside the retort heats up, the escaping gases lift the barrel just slightly and the gases are burned off as they exit.  When the wood inside the inner barrel stop off-gassing, the barrel settles back down and cuts off oxygen getting to the wood inside so it doesn't burn up.  If the holes are in the top of the barrel, enough oxygen still gets into the barrel to turn your charcoal to ash.

That makes a lot of sense. Thank you!
Would it still work the same way if the inner barrel was just an open bottom set onto the "floor" of the outer barrel?

Erika House wrote:That makes a lot of sense. Thank you!
Would it still work the same way if the inner barrel was just an open bottom set onto the "floor" of the outer barrel?

I've done it that way. As long as the inner barrel sits pretty flat in the outer barrel, it works fine.

Excellent explanations, Trace!
John S
PDX OR