The smoke chamber also lessens the force of the down draft by increasing the area through which it passes.
The second vital consideration is the introduction of what are known as a “smoke shelf” and a “smoke chamber.”
The smoke chamber should be lined with fire clay or cement mortar one-half inch thick.
In figure 13-B is shown the throat, the narrow opening between the fireplace and the smoke chamber.
The area in between this and the flue itself is called the smoke chamber.