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OIl Furnace Fumes in House

Furnace Problems

Issue: Combustion/Exhaust Fumes back up into house in basement and goes up through vents.

Conditions When This “Does Not” occur:
• When thermostat is kept at a normal daytime temperature. In fact, when these fumes start occurring (thermostat down at night for example), I simply turn up the thermostat to normal daytime temp and fume issue goes away.
• I shut off thermostat at night (as we go to bed) unless temperature colder than -20C - Then I turn on thermostat in early morning to normal temperature – no problems.

Conditions When it “Does Occur”:
• We like the house coolish at night. Normally I would turn thermostat down at night. Obviously the furnace still comes on but less so, meaning it gets colder downstairs between firings. This is when the fume issue starts.
• Only at night
• Last week I stood at the furnace as my wife turned on thermostat in these colder night time conditions – the smell starts and leaves the furnace immediately it fires up, not just after blowing starts. I reported this to the person from Deeth and White.

• When it began years ago, unless it is really cold I simply shut off the furnace at night and restart cold in the morning – no exhaust issues at all. When we leave house thermostat is either up or off, not turned down.

My Thoughts:
• Clearly this is happening when the temperature in the basement/stack outside is decreased between furnace firings because the issue does not occur at normal set daytime temperatures. The odd part is that when I shut the thermostat off completely and the house gets “really” cold at night, and I turn the furnace on in the morning, no problems - although the difference here is that it stays on until it reaches a high temperature, which can take an hour – getting a chance to heat right up.
• It seems to occur when it is coldish, the thermostat is down, and therefore furnace firing frequency is less often.

One Addition:
• We have exactly the same problem with the hot water heater, although it does not get as bad because it is only on for a very short time.

What I Have Done to this Point:
• 3 Technicians over 5 years – have done the obvious stuff – latest one suggests that distance to outside wall should be 10 feet (which it physically is) but piping to get there is double that.


  • SlamDunk
    SlamDunk Member Posts: 1,590
    edited January 2020
    Furnace make/Model/ and fuel / burner may help folks here help you better. Also, "obvious stuff "is limited to experience levels. Can you list so we don't suggest again?
  • Jamie Hall
    Jamie Hall Member Posts: 23,419
    Step 1. Turn off the furnace and the water heater with their emergency switches.

    Step 2. Leave them off until you can get a qualified technician in there and a qualified chimney sweep to determine the problem and repair it.

    Step 3. If the house is going to get below freezing before that, drain the water and remove things which might be damaged.

    You have a potentially lethal problem here, and no one should be in that place except properly equipped and prepared repair people until it is fixed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ChrisJ
    ChrisJ Member Posts: 15,767
    Please post some pictures of the boiler, smoke pipe and the chimney.

    How well sealed is your house?
    Do you have any big vent hoods over your kitchen stove etc?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    EBEBRATT-Ed Member Posts: 15,607

    You need to take some action on this. Flue gas contains carbon monoxide and it's effects are cumulative
  • jonknights
    jonknights Member Posts: 2
    We have had this for eight years (as long as we have been in the house , which is 30 years old). Have carbon mon. detectors in four locations - they have never registered a problem of any sort and they are all new within the last couple of years.

    As mentioned, when temperature is set at normal daytime temp, we never have issues at all. Given we like it cold at night and depending on the actual coldness outside, I always shut off the furnace at some point during the evening anyway (rather than turning it down).

    Also, don't forget that the Hot Water Heater creates the same issue, meaning it is not likely to be the furnace itself??

    Make: Lincoln 1999
    Motor: Honeywell
    Hot Water Heater: John Wood (new)

    In terms of tech guys - I am not knowledgeable about what they do but they obviously checked everything furnace and draft is around normal - although the latest one suggested the draft was weaker toward the outside wall than near the furnace area.

    What about putting heater in furnace room to keep temperature in there higher so turning down at night doesn't make it cold in that room.


  • SlamDunk
    SlamDunk Member Posts: 1,590
    edited January 2020
    Photos would be very helpful. It sounds like a blockage in chimney but It could be lack of air when both appliances are running. In any case, are your detectors low, like at bed height? I don't think CO rises to the ceiling like smoke.
  • Jellis
    Jellis Member Posts: 228
    Hi Jon,
    if you could post pictures of your unit including venting someone here may be able to spot a problem.
    smell from oil burning equipment in the home is extremely troubling.
    a tech should be able to identify issues that could be causing this.

    Post a picture of your last combustion test as well.
  • Jamie Hall
    Jamie Hall Member Posts: 23,419
    Most CO detectors for homeowners do not detect at a low enough level to protect against long term low level exposure -- which is bad news (just not lethal immediately). But it's your house, and your family...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    rick in Alaska
    HVACNUT Member Posts: 5,858
    I think it's time to get a supervisor to your home. Letting this go for a day is too long, let alone eight years. Ludicrous.
    Do the techs leave combustion analysis printed reports?
    Anyone put a camera up the chimney?
    If your service company can't resolve it pronto, get a new company.
    I've had a long week and I'm in no mood for stupidity.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited January 2020
    HVACNUT said:

    I've had a long week and I'm in no mood for stupidity.

    When would you be in the mood? LOL ..
    Gonna be 60 this weekend...catch up!

    Venting issues (as do others) require sometimes to take in the entire picture. From looking up at the roof for and it's surrounding area for issues, down the chimney for blockages, size, integrity, the flue pipe itself, especially if multiple appliances are connected, combustion, combustion air, cold oil, other appliances in the house possible putting the house in a negative draft state.
    Could be something as simple as a bad/missing cleanout gasket.

    I would like to see a pic, far enough back to see all the flue pipe, as well as if the OP can give us a total height of chimney, from connector in basement to top of chimney.

    A little while ago there was a poster with something like 15'-20' of flue pipe.

    There was an error rendering this rich post.

  • rick in Alaska
    rick in Alaska Member Posts: 1,457
    When the furnace shuts off, can you put your hand in front of the barometric damper and feel heat coming out of it? Or anywhere on the furnace? Especially around the burner. That would indicate a back draft which could be caused by a bad chimney, or something in the house like a vent fan pulling the house in to a negative pressure.
  • vibert_c
    vibert_c Member Posts: 69
    Here is a tale of CO poisoning experienced by my family.

    My mother complained to dad that she was experiencing something similar to a headache but she described it more precisely as if someone put a halo around her head and tightened it up with a ratchet strap. She had to go for a walk around the block to clear the situation.

    Dad had the furnace attended to the very next morning by the original installer.

    They arrived, two of them around 10:30 am.

    Mum called me at work to come home and check things out when they left around 11:00 am

    I took a candle to the basement lit it and turned on the burner.

    At the inspection port at the front of the furnace I discovered the air was not being sucked into the firebox, but blowing out, sufficient to deflect the candle flame.

    I went to the cleanout at the flue, inserted a hand mirror to view up the chimney, to find

    that it was blocked

    I didn’t get back to work that afternoon as it took me three hours to clear a squirrels nest from the chimney.

    This incident has confirmed to my mind that the talent of the service technicians were in those days, (30 yrs ago) no more than a trained monkeys.

    Have you or any of your family ever experienced a tightening of a halo around your head? If so take @Jamie Hall’s advice immediately, do not pass GO, do not collect $100.-

    EBEBRATT-Ed Member Posts: 15,607

    Sounds the the draft may be ok when the chimney is warm but not when its cold.

    Someone needs to check the chimney, it may be oversized, it may have a blockage, it may need a chimney liner. Mabe you should call around and find a good chimney sweep

    Your not supposed to breathe products of combustion
  • captainco
    captainco Member Posts: 796
    How are the oil lines run? Do the water heater and boiler use the same line? Is this a 1- pipe or 2- pipe system. Where is the oil tank. This could be caused by loss of prime and delayed ignition because of the longer off cycle.
    If it was a flue problem it would exist all the time. A burner has the same temperature of flame all the time and the temperature of the flame and the outside temperature create the draft.

    Seems weird that you home would depressurize that much at night to cause a problem and if it did it would be a problem more often,