What is the term for an enclosure that separates a chimney from the living area?

The term for an enclosure that separates a chimney from the living area is known as a chase. A chase serves to protect the chimney from the elements and to improve the aesthetics of the structure. It is typically designed to blend in with the architectural style of the home while providing a barrier that minimizes the cold and heat transfer between the chimney and the living space.

While terms like flue, shroud, and enclosure are associated with chimneys, they refer to different aspects of chimney systems. A flue is the conduit that carries combustion gases away from the fireplace or stove. A shroud may refer to a decorative covering that disguises the top of a chimney or directs the flow of exhaust gases, but it does not specifically refer to the enclosure that separates the chimney from the living area. An enclosure is a broader term that might describe any type of covering, but it lacks the specific function and design intent of a chase. Hence, the chase is the most accurate term in this context.