Abstract: A heat exchanger for a fireplace comprises a tubular grate, a double-walled rectangular, vertical, flat panel located at the back of the fireplace at right angles with the grate tubes, two flat double-walled vertical side panels set at about 45 degrees with respect to the centerline of the fireplace, a zig-zag double-walled panel which extends upwards from the upper side of the back panel to nearly reach the inner surface of the fireplace hood and a double-walled counter panel with angled profile which is so positioned with respect to the zig-zag panel that a progressively narrower throat is formed therebetween for the flames and smoke which rise from the hearth. Due to such tortuous passage of decreasing cross-section for the fire, flame and smoke, the overall height of the exchanger can be reduced so that it can be readily removed from the fireplace masonry structure.