Chimney throat

Chimney throat

That part of a chimney directly above the fireplace where the walls of the flue are brought close together as a means of increasing the draft.

chimney throat, chimney waist

The narrowest portion of a chimney flue, between the gathering (or upward contraction above the fireplace) and the flue proper; often where the damper is located.
References in periodicals archive ?
and through the broad chimney throat, in the late winter evening, ere he stretched himself upon the straw, he looked up to learn the progress of the storm, and, seeing the bright stars of Cassiopeia's chair shining brightly down upon him, fell contentedly asleep.