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is it true

that carbon monoxide is only formed from incomplete combustion.  almost everything that I have read online says that this is so. Even the name implies this. Monoxide, lacking the oxygen atom that would normaly be a bibroduct of combustion as carbon dioxide. But many people in the field for a long time insist that if you drill a hole in a furnace heat exchanger (excluding other problems this would create) you will for sure get CO in the house. Thanks, Michael.


  • JStarJStar Member Posts: 2,668
    edited October 2013

    Yes, it is a byproduct of incomplete combustion. In practice, it is (nearly) impossible to achieve perfect combustion.

    If you have a hole or crack in a modern furnace HX, the higher air pressure of the blower will force air into the lower pressure of the HX, and send all products of combustion through the vent/chimney.

    More commonly, a natural draft appliance with a compromised HX would be able to roll the exhaust out of the burner opening and create CO in the house.
    - Joe Starosielec
  • charliechicagocharliechicago Member Posts: 68
    OK but

    does a properly operating furnace create dangerous levels of CO if they were somehow vented into the living space.
  • charliechicagocharliechicago Member Posts: 68
    I have

    put a CO tester at the outlet of  the flue and had no reading.
  • JStarJStar Member Posts: 2,668

    It depends. I've seen 1 year old furnaces producing enough CO to kill everybody in the house if it ever leaked into the living space. I've also seen an 80 year old furnace running clean enough to not even cause a headache. You may not get CO in the airflow, but more often from chimney spillage.
    - Joe Starosielec
  • charliechicagocharliechicago Member Posts: 68

    But I would think that there has to be a reason for that. I read that overfiring can also cause CO because you get incomplete combustion from the extra gas. Did you find any reason for the CO on the new unit? Thanks, Mike.
  • JStarJStar Member Posts: 2,668

    The one time that I found over 600ppm in the flue of a new furnace was caused by an unsupported gas line putting weight down on the gas manifold. It lifted the end burner up about 1/4", and the flame was hitting the furnace casing around the HX opening. The flame looked perfect by eye.

    I also find A LOT of improperly sized and/or installed liners and vent connectors that cause high CO readings.
    - Joe Starosielec
  • EmpireEmpire Member Posts: 2,343

    Carbon monoxide IS one of the products of combustion.  The goal is to keep it within manfg. specs.  Reducing primary air, results ion an increase on CO.  Incomplete combustion if measured already has a problem and lacking one or more parameters required for complete combustion.  Bacharach has great information as to explain the why and why not's of combustion.  Example; if you achieve excess primary air, your flame will burn cleaner, but loose efficiency.  Please take a look at the web site and it will explain the answers to all your questions.


    Mike T.
  • Jim DavisJim Davis Member Posts: 578
    carbon monoxide production

    Besides combustion, the human body produces carbon monoxide chemically.  Cleaning compounds such as methyline chloride convert to CO in the body and cause CO poisoning.  According to my good friend Albert Donnay, a medical guru on CO poisoning and treatment, womens bodies produce high levels of CO when they are pregnant, time of the month and menepause.  Men beware!   Also chemicals like hydrogen sulfide(battery chargers), cleaning compounds and nitrous oxide can cause all CO Alarms and Analyers to read CO.
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