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Thread: Chemical odor from central heating's chimney

  1. #1

    Default Chemical odor from central heating's chimney

    Hi all,

    I have an outdoor natural gas central heating unit (which also has a built-in AC). On the side of this large box-like unit is a small vent that outputs hot air/gasses. The odor of these gasses has a VERY strong "chemically" smell. Is this normal, or might there be excessive unburnt natural gas mixing with the normal heater vent exhaust? And can this be dangerous?

    Thank you!


  2. #2

    Default Answer to furnace vent odor...

    To save anyone who may read this thread in the future: the smell from the vent was caused by poisonous gasses due to a cracked combustion chamber in the gas furnace.
    There are only two solutions to this problem (that is, if you lived through the carbon monoxide poisoning that this issue causes): replace the combustion chamber (>$1500), or get a new central heating unit (>$4200).
    PS: I'm really somewhat surprised that this HVAC forum didn't know the answer to this critical life and death problem...


  3. #3


    Thanks for posting that.

    BTW, this is first and foremost a plumbing forum. HVAC questions that are are more serious than just replacing the thermostat are often given the standard answer, "Call your HVAC professional."

    PS: Didn't your CO detector go off, alerting you to a hazardous situation?
    Last edited by Verdeboy; 12-26-2008 at 11:59 AM.

  4. #4
    DIY Senior Member burleymike's Avatar
    Join Date
    Nov 2008


    If that smell is coming out of the exhaust what would that have to do with a cracked exchanger? If that smell is coming out of the supply ducts then it makes sense.


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