Nothing, because most "gasses" and "liquids" are both hydrodynamic fluids. Yes they are in different states, but so it ice, magma and glass. All of which is much easier to explain then solar wind xD
What would you expect from the same person that decided to completely block all air into the kiln. Charcoal is made from extremely low airflow fires, he should had blocked the opening and left the tiny chimney alone.
Ryuma actually used a real method for creating charcoal here surprisingly enough. Check out the YouTube channel "primitive technology" he uses the exact same method.