Question: I appreciate you responding to my fireplace problem. (I was the one with smoke coming down the second flue) You mentioned extending the flue. Unfortunately this is not my house, although I certainly am allowed to make any updates I want. I'm looking for a quick fix in the mean time. Would keeping a fire in the lower fireplace work as a quick fix?? Answer: You'll get the same problem, in most cases, with smoke getting sucked down the other unused flue. If both flues are being used, it should be okay. Quick, cheap, temporary solution: place a short section of pipe on the downstairs flue termination to extend the height. Perhaps a chimney sweep could do this for you.