Question: Mr. Hearth, We recently bought a house built in 1959 with fireplace on main floor & basement. The basement fireplace starts to smoke it seems once the room begins to warm up and as the fire goes down. Seems to have good draw initially. The main floor fireplace works fine. There are mature trees surrounding the house. Old owner said, the basement fireplace worked when the house was new, but hasn't for years, I'm thinking trees matured is possibility? Things I tried: extended the chimney 5 ft with pipe, tried cracking basement windows, covering cold air and vents in room, furnace off.---not much success Fireplace Specs: Chimney length= 22ft, chimney dimensions=10X 53/4 (has 6 offset, exit to side of firebox) brick firebox Face opening= 26ht x 36 width. Is this just a poor design with small flue and offset? Chimney approx. 7 ft above roof peak of house with pipe. Give me your best thoughts and advise? Answer: Probably a case of flow reversal, which is more common with lower floor fireplaces. As the fire slows down, the chimney loses the warmth which makes it draw. In addition, basements do not have as many windows and doors so they lack combustion air. Try cracking a window or exploring ways to bring outside air into the fireplace..also, installing glass fireplace doors and closing them when the fire is lower might help the chimney stay warmer and require less air."