Abstract: This is a unique and improved throat for chimneys such as chimneys used in connection with fireplaces which features a complete former damper and throat attached to the sides of the chimney hood portion immediately above the firebox in such manner as to provide a chamber into which downdrafts from the chimney will be directed so as to be diverted back up the chimney and wherein the draft from the firebox or combustion chamber together with smoke will be diverted up the chimney so that if diverted otherwise by downdraft it will enter the air shelf and return up the chimney; the invention is further characterized by the capability of being formed of cardboard or the like in an inexpensive manner which will burn away, and leave the masonry which has been formed thereabout as the final unit; the air shelf is provided with unique cleaning potential through provision of a washing opening.