Historical Siberian Yurt

[Andrei]

Hello,

In "Travels in Kamchatka, during the years 1787 and 1788" by J.-B.B. Lesseps you can find the following description of Tungus (modern Evenki in NE Siberia) yurt:
"The winter yourts are round, and built upon the ground like the summer ones. The walls are constructed of large beams, placed perpendicularly, and the covering is inclined like the roofs among us, with a hole in the top for the evaporation of the smoke. They have a door, the bottom of which is upon a level with the foundation. Some of them have within a kind of corridor, which breaks the column of air, so that the smoke issues more freely."

My question is re. the last sentence:
How does it really look? How does it work? What is that "corridor" and how does it "break the column of air"? Any ideas?
Note: there is NO stove in this kind of yurt, the fire is on the ground.