The inner surface of the smoke chamber should be parge coated smooth with insulating refractory mortar and not inclined more than how many degrees from vertical?

The correct answer is that the inner surface of the smoke chamber should not be inclined more than 40 degrees from vertical. This maximum angle is important for several reasons related to the efficiency and safety of chimney systems.

When the smoke chamber’s walls are vertical or nearly vertical, it allows for better draft and more efficient movement of smoke and combustion gases upward through the chimney. An inclination greater than 40 degrees can hinder the flow of these gases, potentially leading to decreased efficiency and an increased risk of backdrafting or accumulation of creosote, which can lead to chimney fires.

Parging the smoke chamber with insulating refractory mortar not only provides a smooth surface for the proper flow of smoke but also helps to retain heat, further improving the draft. Maintaining the proper angle ensures compliance with established building codes and standards, which are designed to promote both performance and safety in chimney installations.