smoke shelf[′smōk ‚shelf]
A horizontal surface directly behind the throat of a fireplace to prevent downdrafts.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
A concave shelf on the back wall of a smoke chamber, just above the throat, to redirect downdrafts into updrafts on the front wall of a smoke chamber.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.