Abstract: An elongated air manifold is provided to be positioned with the manifold extending across the opening of a fireplace closed by conventional glass doors. The manifold is disposed inward of the glass doors and includes outlet openings spaced longitudinally therealong and a shiftable damper plate for variably opening and closing the outlet openings. The opposite ends of the manifold include air inlet openings with which air ducts opening to the exterior of an associated building are communicated and the air inlet openings of the manifold have valve structures operatively associated therewith for variably opening and closing the air inlet openings. The valve structures and the damper plate may be operated from within the fireplace.