A licensed chimneysweep recently inspected the sole flue in our ~100 year old house. He reported that "buildup is not too bad, but the flue should be cleaned." He also reported that the flue could NOT be cleaned "because two or more appliances share it," i.e. the fireplace on the main floor and the oil furnace in the basement. In the attic there is also evidence of a third appliance sharing the same flue, probably the original wood stove in the kitchen, which is long gone. Any guidance as to what to make of this? It's hard to believe that the flue has never been cleaned.

  • not (presumably) physically impossible to clean, but not something a licensed sweep is going to do, as the use of two appliances on one flue is not up to present safe practices. i.e. if you want to use the fireplace, plan on making there be two flues. Which won't be inexpensive...
    – Ecnerwal
    Commented Nov 24, 2019 at 3:55
  • I presume the issue is that debris from the flue may fall into the oil furnace? If that is the problem, perhaps if the furnace were disconnected it could be done somewhat safely; however, those safety practices are there for a reason. My uncle's house burned to the ground because of an oil furnace flue issue. I'd recommend reconfiguring this to separate flues if possible.
    – peinal
    Commented Nov 24, 2019 at 15:01
  • As well as cleaning, there is the issue that the oil furnace probably has a fan to bring air to the burners. This can potentially push the combustion gasses out the fireplace. We addressed a similar risk (pellet stove and wood stove) by putting a CO detector in the room with the wood stove. Commented Nov 24, 2019 at 17:42


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