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Carbon Monoxide Issues - HELP!

DPB Member Posts: 13
We have a Buderus direct venting high efficiency oil boiler that was installed four years ago. When it was installed, the direct venting (and also combustion air intake) piping were installed and our chimney was demolished.  We have had problems ever since - any time a window is open the gas comes in, and our house had a constant smell.  Recenly, our CO detectors in the house went off.  Fire department came and got positive hits and shut the boiler off.  Heating company came and it turns out the galvanized exhaust pipe was completely rotted.  They replaced with another galvanized since they don't keep SS in stock.  We are going to have it replaced with SS once its available.  After this happened we also ordered a digital CO detector so we could check levels as well if we got another hit. We brought it into the basement and found we are STILL getting CO.  Every time the boiler comes on it spikes into the hundreds.  We have our basement door open a crack right now, which seems to dissipate the CO pretty quickly and our house detectors (with one in the basement) have not gone off again yet.  The heating company has come back and "re-sealed" it several times with more red goop, and has still not fixed the problem.  Someone suggested we put an exterior SS chimney in ($$$).  My question is - will this really solve the problem?  Shouldn't we fix the leaky exhaust pipe issue first?  Will the chimeny work with the blower on the boiler (which seems like it is meant to blow the air out without a chimney)?  Also - aren't we asking for more rotting issues of the chimney as well?  Also, to further compound the issue, the problem is worse after we've been running the dryer, so it seems we could have a negative pressure issue too.  If we put a chimney in, couldn't this be asking for trouble too then? Meaning wouldn't the negative pressure draw air in from the barometric regulator thing?  Sigh.  I'm so stressed and fed up with this issue that I'm ready to turn to electric heat.  Please help!!  Should I be pushing the heating company more, or is there really nothing else they can do?  Is the Chimney the only way to solve this problem?


  • DPB
    DPB Member Posts: 13

    Here's a photo of the install if it helps. Note the reading in the hundreds on the CO detector (boiler was on)
  • Zman
    Zman Member Posts: 7,569

    Please turn of the power and gas to the boiler.

    This should assure that you will be alive in the morning to post more pictures and the model number of the boiler.

    There is nothing normal about what is going on here.

    Break out the heavy quilts and turn it off now!!!

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • kcopp
    kcopp Member Posts: 4,432
    Something is amiss....

    here. For starters I'm not sure this is installed 100% right. The Buderus boiler that direct vent (not a fan of them btw) come w/ a special vent that is insulated. Second the CO detector is too close to the boiler. Instructions say it should be 5' away.

     What model is this? Was it set up w/ combustion equipment? What were the numbers on the test?

    I think you are getting some cross contamination. Post some more pix of the vent and the hood from outside.
  • Gordy
    Gordy Member Posts: 9,546
    Barometric damper

    Is not suppose to be on the exhaut pipe.

    Why would you use one with a fresh air intake??

    I think exhaust venting is to long of a run with improper pitch also.

    Agree with Carl shut it down now!!
  • Weezbo
    Weezbo Member Posts: 6,232
    edited November 2013
    i have never seen a Buderus piped that way,

    that might be some sort of "Kit" for an Le boiler buh even then the parts it should have on it were that the case are non existent.

    the things to look for are the termination of the make up air outside the building

    i think it is in an inside corner outside and that is a problem

    it sounds as though that is blocked off .

    the stack itself is not supposed to be blocked off in any way , nor withing certain distances of other vents openable doors and windows, if it has a soffit above it then that is another problem when ever a barometric is set into an intake air it is in the fully closed position and it only allows indoor air when it is super cold outside to mix with preconditioned air ,

    that would mean you may have inside air going into the stack thru the burner it cant go backwards thru the make up so it must be leaking out the door if it isnt the stack .

    the door is under the cowling which just comes away a picture of that removed and the lash up to the burner would make it even easier to see what is going on inside the building ,

    a picture of the outside where the vent comes out the wall would be a good thing .

    because i think if what we see in this picture is indicative of what problems exist then outside there may be even more ...

    and under the cowling in front of the boiler .

    if your circ is installed on its own switch you could turn the boiler off and let the circ run ..that way moving water is less likely to freeze,

    auxillary electric heat is your safe bet . for now ...

    i cannot read the numbers on the co detector only thing is the carbon monoxide levels of 100 to 200ppm are not unheard of within the combustion chamber or stack . in the open atmosphere of the room thats a whole different deal.

    one thing more holes between the boiler room and the living area should be sealed you get someone who does energy ratings to come do a blower door on your whole house ..and look for the report in your documents of the house when you bought it.

    i think it will say who did the tests contact him and have him come over he can pin point the size and place they exist.

    a boiler consumes house loads of air an hour of burn . so it can cause other appliances to starve for combustion air or cause back drafts and holes that are not sealed can cause differential pressure plane problems ... they can also create stack effects that cause more problems than you may be aware of at this time.


    see if you can find someone else ( who installs and services Buderus oil fired boilers) to come by as well , because i am not particularly sold on the idea that these things that i see are the only problems that exist .
  • JohnNY
    JohnNY Member Posts: 3,230

    If your plumber can't address this problem, then call a reputable chimney contractor and get his take on it. Venting is not every plumber's forté.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • DPB
    DPB Member Posts: 13
    First to answer the questions

    This is a Buderus G125/21BE.  The CO detector you see is the one we bought and we just put it on top - I would think even with it being too close to the boiler it should still read zero all the time?  Or is it normal for some level of leakage of CO from the boiler at all times?

    Anyway re: the damper - we were the first installation of this type in our City.  When the fire marhall did the inspection he wanted a damper on the exhaust.  The installer didn't want to put one on there since it doesn't need it, so they "compromised" by putting one on the intake.  The sloped pipe is the intake, the pipe that goes straight up and out is the exhaust.  I'll post pics of the exterior and more of the interior in a second.

    Let me know if you need more photos....I have an iphone so it's easy to post.  We're going to call the installer again today to come out...having suggestions/recommendations for them would be fine.  Also, I have a friend who lives a half hour away with Buderus boilers who has a heating company he likes and says is really good - should I have them look at it too?
  • DPB
    DPB Member Posts: 13

    Here are more photos

    Exterior and more of interior
  • JohnNY
    JohnNY Member Posts: 3,230

    "The installer didn't want to put one on there since it doesn't need it, so they 'compromised' by putting one on the intake"


    You might want to give your friend's plumber a call and give your guy the day off today.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • Weezbo
    Weezbo Member Posts: 6,232
    edited November 2013
    oh My ..

    the installer should have mentioned that he is certified and trained to install the boiler.

    and if the firemarshall wanted to sabotage the work then he needed to take that up with the manufacturers.

    where i live , 3 concrete blocks is 4 feet and i see soot on the walls and that appears to be an open able window. that is a blue flame boiler . This sounds like a bad joke ... and looks it too.

    they use concentric vents . when the Fire Marshall designed this lash up i think he needed to run that by the people who do all the research listing and development of the equipment... why would they spend such a hefty amount of funds doin all that if he

    is going to attempt to engineer it on the spot ? like i said i have never piped a buderus that way ...who told the installer it was right to do that?

    i am hard pressed to think it was the instructor of the class he took ...

  • DPB
    DPB Member Posts: 13
    Ok so...

    What is the recommendation? I'm not trying to bash - just want help figuring out what is wrong. We could feel air coming in to the damper so we put a makeshift "cap" on it - still getting CO hits. Other suggestions?
  • JohnNY
    JohnNY Member Posts: 3,230

    Venting specs on Page 18 here call for a barometric damper on the exhaust when venting vertically, and no barometric when venting to a side wall:

    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    the air

    Intake is installed wrong. It is too close to the exhaust to be above the exhausts centerline. You're sucking in exhaust and with the Aerocowl term the damper on the intake pipe is not supposed to be there. Making things even worse spilling exhaust into the basement
  • Gordy
    Gordy Member Posts: 9,546
    edited November 2013
    Horizontal venting

    Operates under positive pressure. Unlike vertical venting.

    I suspect that the vent is not sealed properly as the install manual indicates. And cross contamination with the intake damper that should not be there.

    Correction to my first post I miss spoke meant to say intake not exhaust about the installed damper.

  • kcopp
    kcopp Member Posts: 4,432
    edited November 2013
    Chimneys are great...

    and they generally don't break. From what I have w/ direct vent oil experience they are pretty finicky to outdoor temps as the oil atomizes poorer at lower temps.

    I think plain and simple this burner was not set up properly. As another poster mentioned you MUST get factory training to even be sold this boiler. Is the installer trained? Was  there a combustion test done? There should be a slip of paper there if so.... The black steak up the side of the house makes me think not....

    The intake damper needs to be there to Balance out the outdoor drafts. There could be better separation w/ the intake. The vent pipe looks like its aluminum... again Pretty sure it needs to be stainless or 24 ga.  galvy.

    You said it rotted out? how old is the install? Was it cleaned if over 1 yr old?

    Curious about where is this install?
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    not with

    The Aerocowl exhaust term Kevin. I and O specifically states to not use it. Been blue flame certified 5 years now.
  • billtwocase
    billtwocase Member Posts: 2,385
    widow maker

    this is one poor install. Never a draft control on a direct vent to start with. That is where you CO is coming from, and needs to be set up properly with instruments. Shut it down, and stay alive
  • DPB
    DPB Member Posts: 13

    So had the heating technician here this morning - we confirmed that exhaust is being sucked into the basement via the damper (at my suggestion to check thanks to you all!). He wasn't sure what to do and said he needed to check with his boss and will get back to us tomorrow. I will keep you updated. Oh but he did say that the damper was required in case we get many feet of snow blocking the intake..? We are in MA.
  • billtwocase
    billtwocase Member Posts: 2,385
    true yes and no

    there is a vacuum breaker for the air intake, not a draft control on the exhaust. He should at least put a plug in that "T" where it is for now
  • kcopp
    kcopp Member Posts: 4,432
    ok... another reason...

    why I stopped installing Direct vent oil. I feel we the installers are the Lab Rats for these. They are learning as they go.

    Go w/ the SS chimney!
  • DPB
    DPB Member Posts: 13

    The damper thing is on the intake not the exhaust. In playing with it we realized it is even worse when we are running the clothes drier (CO shoots up).
  • kcopp
    kcopp Member Posts: 4,432
    so there is no....

    draft. UGH! Seriously. Get some quotes on an exterior 6" SS All fuel chimney.
  • Weezbo
    Weezbo Member Posts: 6,232
    this boiler is more powerful than a gas burning

    appliance . oil has some very distinct abilities and as a blue flame it is all over making water, heat .

    it is on a , "Ho Nuffa Laval"...

    i did not designe this burner yet i hassled with buderus to bring it and an other control here for a couple years before it ever showed up.

    one of the buderus instructors told me in front of the Class that another buderus beyond this , did not exist .

    he sad he went to Germany to get his training ..and then said that they have 1500 people working there at Buderus and did we know what that means ,

    so i said yah ,

    they sent you here to pick our brains because we Know what we are doing.

    and then i told him i can HAVE a picture of the boiler on his lap top at lunch time by going home and sending him a picture of it to his e mail.

    that other boiler is like 106 or 111 % eff rating .

    whatever... thing is , combustion tests are not done with the door open etc for a number of reasons.

    a draw band could bring in more outside air , and at least stop the burner from hoovering every available source of intake air ...which would be a Plus ...

    the negative side is that will change whatever settings he has it at that could be a minus ..

    when your tech arrives if he were to band the place the T exists and take new readings and adjust the fuel pressure after cleaning the combustion chamber , that would likely clean up the co issues ....in the room.

    do not leave it like that though , get the right parts and pieces , hook it up right. and apply for a new inspection ...so that the AHJ can see when it is done correctly .

    ... he isnt the enemy . there are just some things he did not know . there are experiences the company does not want Americans and Canadians to have ...

    they maybe already made those mistakes. Yah?



    this boiler 's burner has ways to go about things very specifically .

    tuning the high co in it produced , gives co2 readings in the 14. + range ...

    i just hate to say put a draw band on the intake instead of the T , because , even though i did not tune it up the atomization is way up scale . and Bang! is Not good, with fuel gas .

    as the burn is "Tuned" with oil pump pressure , he likely did not get enough air to begin with , unless the door was open to that room with some communication to the outside air through an open window or door.

    that is a low Nox burner too by the way ...
  • icesailor
    icesailor Member Posts: 7,265
    edited November 2013
    Vent Termintion:

    The vent termination is also too close to the ground. .3 meters (12") plus the NOAA ?normal" highest winter single storm depth for that area.

  • Zman
    Zman Member Posts: 7,569

    Please tell Me that you have not been sleeping in the house with this problem going on.

    Has anyone ever done a combustion analysis on the boiler?

    As a perspective, if you had CO readings over 100 INSIDE the flue, your boiler is not running right and should be tuned. You are over 100 in the house!

    The black mark on the siding tells me you have a serious problem. The CO detector says you have a very serious problem. Don't rely on a cheap consumer CO detector to save you. Turn it off!

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • DPB
    DPB Member Posts: 13
    Yes, well....

    we are still in the house.  We have whole-house detectors, and nothing has gone off *yet*.  We are keeping the basement door open for now, and it seems to air out everything for now (not ideal obviously).   We are trying to be as safe as possible and not being stupid about it - but the other thing to point out is that we've been living with this arrangement for four almost five years now, and only now are realizing the problem of small amounts of CO getting sucked into the basement because we just bought a CO detector with number readout after the big hit (From the exhaust pipe being completely eaten away by acid).  That was the issue that lead to the discovery of this issue.

    Anyway, we are waiting for the heating company to get back to us - I'm going to call them soon for an update.  I think we're also going to get a second opinion on  what needs to be done to fix all of this.  Problem is, if we get someone else to fix it, then we'll have to pay the cost (and we can't afford that)....if we keep the same installer to fix it though, then chances are they'll do the bare minimum.  Not sure how to handle that.

    Anyway...I'll keep you all updated on this.  And thank you SO MUCH for the advice - if it weren't for the post on here we wouldn't have ever figured out the issue with the intake damper sucking in CO into the basement and we'd still be searching for ways to seal up the exhaust pipe and scratching our heads when that (yet again) didn't solve the problem....

    Oh and to the other post re: snow depth - I think you're right about that one too, seeing as after the snow storm we got last winter we had to shovel out our exhaust pipe in the morning (was buried in a snow drift).

    Boy if I could go back and keep that damn masonry chimney....
  • DPB
    DPB Member Posts: 13
    I should add

    we have the bulkhead door to the basement (goes directly to the outside) open, not the door to the upstairs.  So the CO usually only has been accumulatiing in the basement.  What it did in previous years though I don't know...although it obviously couldn't have gone above the limits of the detector or I would think it would have gone off.  I wonder though if we've had constant low level CO in our house now for years....

    If we had other options (family in area) we would take advantage of them, but unfortunately we do not and we have two children under the age of 3.  Again - we are trying to be as safe as possible.....and trying to get the problem fixed!!
  • DPB
    DPB Member Posts: 13
    Gah! One more response

    Yes they did do a combustion chamber analysis when they first installed the boiler and removed two of the baffle pairs when they did it.  That was back when they installed it.  We have aluminum siding, and so we have been wondering if the exhaust is slowly eating away at that...thus making the dark color above (and perhaps not poor burning characteristics?)
  • Gordy
    Gordy Member Posts: 9,546
    Just so ya know

    Carbon monoxide poisoning

    From Wikipedia, the free encyclopedia

    Carbon monoxide poisoning

    Classification and external resources

    Spacefilling model of a carbon monoxide molecule

    ICD-10 T58

    ICD-9 986

    DiseasesDB 2020

    MedlinePlus 002804

    eMedicine emerg/817

    MeSH C21.613.455.245

    Carbon monoxide poisoning occurs after enough inhalation of carbon monoxide (CO). Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect. Carbon monoxide is a product of incomplete combustion of organic matter due to insufficient oxygen supply to enable complete oxidation to carbon dioxide (CO2). It is often produced in domestic or industrial settings by older motor vehicles and other gasoline-powered tools, heaters, and cooking equipment. Exposures at 100 ppm or greater can be dangerous to human health.[1]

    Symptoms of mild acute poisoning include lightheadedness, confusion, headaches, vertigo, and flu-like effects; larger exposures can lead to significant toxicity of the central nervous system and heart, and even death. Following acute poisoning, long-term sequelae often occur. Carbon monoxide can also have severe effects on the fetus of a pregnant woman. Chronic exposure to low levels of carbon monoxide can lead to depression, confusion, and memory loss. Carbon monoxide mainly causes adverse effects in humans by combining with hemoglobin to form carboxyhemoglobin (HbCO) in the blood. This prevents hemoglobin from releasing oxygen in tissues, effectively reducing the oxygen-carrying capacity of the blood, leading to hypoxia. Additionally, myoglobin and mitochondrial cytochrome oxidase are thought to be adversely affected. Carboxyhemoglobin can revert to hemoglobin, but the recovery takes time because the HbCO complex is fairly stable.

    Treatment of poisoning largely consists of administering 100% oxygen or providing hyperbaric oxygen therapy, although the optimum treatment remains controversial.[2] Oxygen works as an antidote as it increases the removal of carbon monoxide from hemoglobin, in turn providing the body with normal levels of oxygen. The prevention of poisoning is a significant public health issue. Domestic carbon monoxide poisoning can be prevented by early detection with the use of household carbon monoxide detectors. Carbon monoxide poisoning is the most common type of fatal poisoning in many countries.[3] Historically, it was also commonly used as a method to commit suicide, usually by deliberately inhaling the exhaust fumes of a running car engine. Modern automobiles, even with electronically-controlled combustion and catalytic converters, can still produce levels of carbon monoxide which will kill if enclosed within a garage or if the tailpipe is obstructed (for example, by snow) and exhaust gas cannot escape normally. Carbon monoxide poisoning has also been implicated as the cause of apparent haunted houses; symptoms such as delirium and hallucinations have led people suffering poisoning to think they have seen ghosts or to believe their house is haunted.[4]

    Contents [hide]

    1 Signs and symptoms

    1.1 Acute poisoning

    1.2 Chronic poisoning

    2 Causes

    3 Pathophysiology

    3.1 Hemoglobin

    3.2 Myoglobin

    3.3 Cytochrome oxidase

    3.4 Central nervous system effects

    3.5 Pregnancy

    4 Diagnosis

    4.1 Differential diagnosis

    4.2 Detection in biological specimens

    5 Prevention

    5.1 Carbon monoxide detector recommendations for buildings

    5.2 Legal requirements

    5.3 Equipment maintenance

    5.4 Recommended World Health Organisation (WHO) Air Quality guidelines for Europe 2000

    5.5 Recommended WHO European Guidelines for Indoor Air Quality 2010

    6 Treatment

    6.1 Hyperbaric oxygen

    6.2 Other

    7 Epidemiology

    7.1 Suicide

    8 See also

    9 References

    10 External links

    Signs and symptoms[edit]

    Carbon monoxide is toxic to all aerobic forms of life. It is easily absorbed through the lungs.[5] Inhaling even relatively small amounts of the gas can lead to hypoxic injury, neurological damage, and even death. Different people and populations may have a different carbon monoxide tolerance levels.[6] On average, exposures at 100 ppm or greater is dangerous to human health.[1] In the United States, the OSHA limits long-term workplace exposure levels to less than 50 ppm averaged over an 8-hour period;[7][8] in addition, employees are to be removed from any confined space if an upper limit ("ceiling") of 100 ppm is reached.[9] Carbon monoxide exposure may lead to a significantly shorter life span due to heart damage.[10] The carbon monoxide tolerance level for any person is altered by several factors, including activity level, rate of ventilation, a pre-existing cerebral or cardiovascular disease, cardiac output, anemia, sickle cell disease and other hematological disorders, barometric pressure, and metabolic rate.[11][12][13]

    The acute effects produced by carbon monoxide in relation to ambient concentration in parts per million are listed below:[14][15]

    Concentration Symptoms

    35 ppm (0.0035%) Headache and dizziness within six to eight hours of constant exposure

    100 ppm (0.01%) Slight headache in two to three hours

    200 ppm (0.02%) Slight headache within two to three hours; loss of judgment

    400 ppm (0.04%) Frontal headache within one to two hours

    800 ppm (0.08%) Dizziness, nausea, and convulsions within 45 min; insensible within 2 hours

    1,600 ppm (0.16%) Headache, tachycardia, dizziness, and nausea within 20 min; death in less than 2 hours

    3,200 ppm (0.32%) Headache, dizziness and nausea in five to ten minutes. Death within 30 minutes.

    6,400 ppm (0.64%) Headache and dizziness in one to two minutes. Convulsions, respiratory arrest, and death in less than 20 minutes.

    12,800 ppm (1.28%) Unconsciousness after 2–3 breaths. Death in less than three minutes.

    Acute poisoning[edit]

    The main manifestations of carbon monoxide poisoning develop in the organ systems most dependent on oxygen use, the central nervous system and the heart.[7] The initial symptoms of acute carbon monoxide poisoning include headache, nausea, malaise, and fatigue.[16] These symptoms are often mistaken for a virus such as influenza or other illnesses such as food poisoning or gastroenteritis.[17] Headache is the most common symptom of acute carbon monoxide poisoning; it is often described as dull, frontal, and continuous.[18] Increasing exposure produces cardiac abnormalities including fast heart rate, low blood pressure, and cardiac arrhythmia;[19][20] central nervous system symptoms include delirium, hallucinations, dizziness, unsteady gait, confusion, seizures, central nervous system depression, unconsciousness, respiratory arrest, and death.[21][22] Less common symptoms of acute carbon monoxide poisoning include myocardial ischemia, atrial fibrillation, pneumonia, pulmonary edema, high blood sugar, lactic acidosis, muscle necrosis, acute kidney failure, skin lesions, and visual and auditory problems.[19][23][24][25]

    One of the major concerns following acute carbon monoxide poisoning is the severe delayed neurological manifestations that may occur. Problems may include difficulty with higher intellectual functions, short-term memory loss, dementia, amnesia, psychosis, irritability, a strange gait, speech disturbances, Parkinson's disease-like syndromes, cortical blindness, and a depressed mood.[17][26] Depression may even occur in those who did not have pre-existing depression.[27] These delayed neurological sequelae may occur in up to 50% of poisoned people after 2 to 40 days.[17] It is difficult to predict who will develop delayed sequelae; however, advanced age, loss of consciousness while poisoned, and initial neurological abnormalities may increase the chance of developing delayed symptoms.[28]

    One classic sign of carbon monoxide poisoning is more often seen in the dead rather than the living – people have been described as looking pink-cheeked and healthy. However, since this "cherry-red" appearance is common only in the deceased, and is unusual in living people, it is not considered a useful diagnostic sign in clinical medicine. In pathological (autopsy) examination the ruddy appearance of carbon monoxide poisoning is notable because unembalmed dead persons are normally bluish and pale, whereas dead carbon-monoxide poisoned persons may simply appear unusually lifelike in coloration.[29][30][31] The colorant effect of carbon monoxide in such postmortem circumstances is thus analogous to its use as a red colorant in the commercial meat-packing industry.

    Chronic poisoning[edit]

    Chronic exposure to relatively low levels of carbon monoxide may cause persistent headaches, lightheadedness, depression, confusion, memory loss, nausea and vomiting.[32] It is unknown whether low-level chronic exposure may cause permanent neurological damage.[17] Typically, upon removal from exposure to carbon monoxide, symptoms usually resolve themselves, unless there has been an episode of severe acute poisoning.[32] However, one case noted permanent memory loss and learning problems after a 3-year exposure to relatively low levels of carbon monoxide from a faulty furnace.[33] Chronic exposure may worsen cardiovascular symptoms in some people.[32] Chronic carbon monoxide exposure might increase the risk of developing atherosclerosis.[34][35] Long-term exposures to carbon monoxide present the greatest risk to persons with coronary heart disease and in females who are pregnant.[36]


    Concentration Source

    0.1 ppm Natural atmosphere level (MOPITT)[37]

    0.5 to 5 ppm Average level in homes[38]

    5 to 15 ppm Near properly adjusted gas stoves in homes[38]

    100 to 200 ppm Exhaust from automobiles in the Mexico City central area[39]

    5,000 ppm Exhaust from a home wood fire[40]

    7,000 ppm Undiluted warm car exhaust without a catalytic converter[40]

    Carbon monoxide is a product of combustion of organic matter under conditions of restricted oxygen supply, which prevents complete oxidation to carbon dioxide (CO2). Sources of carbon monoxide include cigarette smoke, house fires, faulty furnaces, heaters, wood-burning stoves, internal combustion vehicle exhaust, electrical generators, propane-fueled equipment such as portable stoves, and gasoline-powered tools such as leaf blowers, lawn mowers, high-pressure washers, concrete cutting saws, power trowels, and welders.[17][32][41][42][43][44][45] Exposure typically occurs when equipment is used in buildings or semi-enclosed spaces.[17]

    Poisoning may also occur following the use of a self-contained underwater breathing apparatus (SCUBA) due to faulty diving air compressors.[46] Riding in pickup trucks has led to poisoning in children.[47] Idling automobiles with the exhaust pipe blocked by snow has led to the poisoning of car occupants.[48] Generators and propulsion engines on boats, especially houseboats, has resulted in fatal carbon monoxide exposures.[49][50] As part of the Holocaust during World War II, German Nazis used gas vans to kill an estimated 700,000 prisoners by carbon monoxide poisoning. This method was also used in the gas chambers of several death camps.[51]

    Another source of poisoning is exposure to the organic solvent dichloromethane, found in some paint strippers,[52] as the metabolism of dichloromethane produces carbon monoxide.[53][54][55] In most light aircraft and some cars the cabin heating system comprises a shroud around the exhaust.[citation needed] Any perforation between the exhaust manifold and shroud can result in exhaust gases reaching the cabin. In caves carbon monoxide can build up in enclosed chambers due to the presence of decomposing organic matter.[56]


    The precise mechanisms by which the effects of carbon monoxide are induced upon bodily systems, are complex and not yet fully understood.[16] Known mechanisms include carbon monoxide binding to hemoglobin, myoglobin and mitochondrial cytochrome oxidase, and carbon monoxide causing brain lipid peroxidation.[21][29][57]


    Carbon monoxide shifts the oxygen-dissociation curve to the left.

    Carbon monoxide has a higher diffusion coefficient compared to oxygen and the only enzyme in the human body that produces carbon monoxide is heme oxygenase which is located in all cells and breaks down heme. Under normal conditions carbon monoxide levels in the plasma are approximately 0 mmHg because it has a higher diffusion coefficient and the body easily gets rid of any CO made.[58] When CO is not ventilated it binds to hemoglobin, which is the principal oxygen-carrying compound in blood; this produces a compound known as carboxyhemoglobin. The traditional belief is that carbon monoxide toxicity arises from the formation of carboxyhemoglobin, which decreases the oxygen-carrying capacity of the blood and inhibits the transport, delivery, and utilization of oxygen by the body. The affinity between hemoglobin and carbon monoxide is approximately 230 times stronger than the affinity between hemoglobin and oxygen so hemoglobin binds to carbon monoxide in preference to oxygen.[29][59][60]

    Hemoglobin is a tetramer with four oxygen binding sites. The binding of carbon monoxide at one of these sites increases the oxygen affinity of the remaining three sites, which causes the hemoglobin molecule to retain oxygen that would otherwise be delivered to the tissue.[57] This situation is described as carbon monoxide shifting the oxygen dissociation curve to the left.[29] Because of the increased affinity between hemoglobin and oxygen during carbon monoxide poisoning, the blood oxygen content is increased. But because all the oxygen stays in the hemoglobin, none is delivered to the tissues. This causes hypoxic tissue injury.[17] Hemoglobin acquires a bright red color when converted into carboxyhemoglobin, so poisoned cadavers and even commercial meats treated with carbon monoxide acquire an unnatural reddish hue.


    Carbon monoxide also binds to the hemeprotein myoglobin. It has a high affinity for myoglobin, about 60 times greater than that of oxygen.[17] Carbon monoxide bound to myoglobin may impair its ability to utilize oxygen.[29] This causes reduced cardiac output and hypotension, which may result in brain ischemia.[17] A delayed return of symptoms have been reported. This results following a recurrence of increased carboxyhemoglobin levels; this effect may be due to a late release of carbon monoxide from myoglobin, which subsequently binds to hemoglobin.[3]

    Cytochrome oxidase[edit]

    Another mechanism involves effects on the mitochondrial respiratory enzyme chain that is responsible for effective tissue utilization of oxygen. Carbon monoxide binds to cytochrome oxidase with less affinity than oxygen, so it is possible that it requires significant intracellular hypoxia before binding.[61] This binding interferes with aerobic metabolism and efficient adenosine triphosphate synthesis. Cells respond by switching to anaerobic metabolism, causing anoxia, lactic acidosis, and eventual cell death.[62] The rate of dissociation between carbon monoxide and cytochrome oxidase is slow, causing a relatively prolonged impairment of oxidative metabolism.[16]

    Central nervous system effects[edit]

    The mechanism that is thought to have a significant influence on delayed effects involves formed blood cells and chemical mediators, which cause brain lipid peroxidation (degradation of unsaturated fatty acids). Carbon monoxide causes endothelial cell and platelet release of nitric oxide, and the formation of oxygen free radicals including peroxynitrite.[16] In the brain this causes further mitochondrial dysfunction, capillary leakage, leukocyte sequestration, and apoptosis.[63] The result of these effects is lipid peroxidation, which causes delayed reversible demyelinization of white matter in the central nervous system known as Grinker myelinopathy, which can lead to edema and necrosis within the brain.[57] This brain damage occurs mainly during the recovery period. This may result in cognitive defects, especially affecting memory and learning, and movement disorders. These disorders are typically related to damage to the cerebral white matter and basal ganglia.[63][64] Hallmark pathological changes following poisoning are bilateral necrosis of the white matter, globus pallidus, cerebellum, hippocampus and the cerebral cortex.[1][17][65]


    Carbon monoxide poisoning in pregnant women may cause severe adverse fetal effects. Poisoning causes fetal tissue hypoxia by decreasing the release of maternal oxygen to the fetus. Carbon monoxide also crosses the placenta and combines with fetal hemoglobin, causing more direct fetal tissue hypoxia. Additionally, fetal hemoglobin has a 10 to 15% higher affinity for carbon monoxide than adult hemoglobin, causing more severe poisoning in the fetus than in the adult.[3] Elimination of carbon monoxide is slower in the fetus, leading to an accumulation of the toxic chemical.[66] The level of fetal morbidity and mortality in acute carbon monoxide poisoning is significant, so despite mild maternal poisoning or following maternal recovery, severe fetal poisoning or death may still occur.[67]


    Finger tip Carboxyhemoglobin saturation monitor (SpCO%). Note: This is not the same as a pulse oximeter (SpO2%), although some models (such as this one) do measure both the oxygen and carbon monoxide saturation.

    Breath CO monitor displaying carbon monoxide concentration of an exhaled breath sample (in ppm) with its corresponding percent concentration of carboxyhemoglobin.

    As many symptoms of carbon monoxide poisoning also occur with many other types of poisonings and infections (such as the flu), the diagnosis is often difficult.[55][68] A history of potential carbon monoxide exposure, such as being exposed to a residential fire, may suggest poisoning, but the diagnosis is confirmed by measuring the levels of carbon monoxide in the blood. This can be determined by measuring the amount of carboxyhemoglobin compared to the amount of hemoglobin in the blood.[17] Carbon monoxide is produced naturally by the body as a byproduct of converting protoporphyrin into bilirubin. This carbon monoxide also combines with hemoglobin to make carboxyhemoglobin, but not at toxic levels.[17] The ratio of carboxyhemoglobin to hemoglobin molecules in an average person may be up to 5%, although cigarette smokers who smoke two packs/day may have levels up to 9%.[69]

    As people may continue to experience significant symptoms of CO poisoning long after their blood carboxyhemoglobin concentration has returned to normal, presenting to examination with a normal carboxyhemoglobin level (which may happen in late states of poisoning) does not rule out poisoning.[70]

    A CO-oximeter is used to determine carboxyhemoglobin levels.[71][72] Pulse CO-oximeters estimate carboxyhemoglobin with a non-invasive finger clip similar to a pulse oximeter.[73] These devices function by passing various wavelengths of light through the fingertip and measuring the light absorption of the different types of hemoglobin in the capillaries.[74]

    The use of a regular pulse oximeter is not effective in the diagnosis of carbon monoxide poisoning as people suffering from carbon monoxide poisoning may have a normal oxygen saturation level on a pulse oximeter.[75] This is due to the carboxyhemoglobin being misrepresented as oxyhemoglobin.[76]

    Breath CO monitoring offers a viable alternative to pulse CO-oximetry. Carboxyhemoglobin levels have been shown to have a strong correlation with breath CO concentration.[77][78] However, many of these devices require the user to inhale deeply and hold their breath to allow the CO in the blood to escape into the lung before the measurement can be made. As this is not possible in a nonresponsive patient, these devices are not appropriate for use in on-scene emergency care detection of CO poisoning.

    Differential diagnosis[edit]

    There are many conditions to be considered in the differential diagnosis of carbon monoxide poisoning.[7][22] The earliest symptoms, especially from low level exposures, are often non-specific and readily confused with other illnesses, typically flu-like viral syndromes, depression, chronic fatigue syndrome, chest pain, and migraine or other headaches.[79] Carbon monoxide has been called a "great mimicker" due to the presentation of poisoning being diverse and nonspecific.[7] Other conditions included in the differential diagnosis include acute respiratory distress syndrome, altitude sickness, lactic acidosis, diabetic ketoacidosis, meningitis, methemoglobinemia, or opioid or toxic alcohol poisoning.[22]

    Detection in biological specimens[edit]

    Carbon monoxide may be quantitated in blood using spectrophotometric methods or chromatographic techniques in order to confirm a diagnosis of poisoning in a person or to assist in the forensic investigation of a case of fatal exposure. Carboxyhemoglobin blood saturations may range up to 8–10% in heavy smokers or persons extensively exposed to automotive exhaust gases. In symptomatic poisoned people they are often in the 10–30% range, while persons who succumb may have postmortem blood levels of 30–90%.[80][81]


    Carbon Monoxide detector connected to a North American power outlet

    Carbon monoxide detector recommendations for buildings[edit]

    Prevention remains a vital public health issue, requiring public education on the safe operation of appliances, heaters, fireplaces, and internal-combustion engines, as well as increased emphasis on the installation of carbon monoxide detectors.[5] Carbon monoxide is tasteless and odourless so can not be detected by smell.[82]

    The United States Consumer Product Safety Commission has stated, "carbon monoxide detectors are as important to home safety as smoke detectors are," and recommends each home have at least one carbon monoxide detector, and preferably one on each level of the building.[83] These devices, which are relatively inexpensive[84] and widely available, are either battery- or AC-powered, with or without battery backup.[85] In buildings, carbon monoxide detectors are usually installed around heaters and other equipment. If a relatively high level of carbon monoxide is detected, the device sounds an alarm, giving people the chance to evacuate and ventilate the building.[84][86] Unlike smoke detectors, carbon monoxide detectors do not need to be placed near ceiling level.[87]

    The use of carbon monoxide detectors has been standardized in many areas. In the USA, NFPA 720-2009,[88] the carbon monoxide detector guidelines published by the National Fire Protection Association, mandates the placement of carbon monoxide detectors/alarms on every level of the residence, including the basement, in addition to outside sleeping areas. In new homes, AC-powered detectors must have battery backup and be interconnected to ensure early warning of occupants at all levels.[88] NFPA 720-2009 is the first national carbon monoxide standard to address devices in non-residential buildings. These guidelines, which now pertain to schools, healthcare centers, nursing homes and other non-residential buildings, includes three main points:[88]

    1. A secondary power supply (battery backup) must operate all carbon monoxide notification appliances for at least 12 hours,

    2. Detectors must be on the ceiling in the same room as permanently installed fuel-burning appliances, and

    3. Detectors must be located on every habitable level and in every HVAC zone of the building.

    Legal requirements[edit]

    The NFPA standard is not necessarily enforced by law. As of April 2006, the U.S. state of Massachusetts require detectors to be present in all residences with potential CO sources, regardless of building age and whether they are owner-occupied or rented.[89] This is enforced by municipal inspectors, and was inspired by the death of 7-year-old Nicole Garofalo in 2005 due to snow blocking a home heating vent.[90] Other jurisdictions may have no requirement or only mandate detectors for new construction or at time of sale.

    Despite similar deaths in vehicles with clogged exhaust pipes (for example in the Northeastern United States blizzard of 1978 and February 2013 nor'easter) and the commercial availability of the equipment, there is no legal requirement for automotive CO detectors.

    Equipment maintenance[edit]

    Gas organizations will often recommend to get gas appliances serviced at least once a year.[91]

    Recommended World Health Organisation (WHO) Air Quality guidelines for Europe 2000[edit]

    The following guideline values (ppm values rounded) and periods of time-weighted average exposures have been determined in such a way that the carboxyhaemoglobin (COHb) level of 2.5% is not exceeded, even when a normal subject engages in light or moderate exercise:

    100 mg/m3 (87 ppm) for 15 min

    60 mg/m3 (52 ppm) for 30 min

    30 mg/m3 (26 ppm) for 1 h

    10 mg/m3 (9 ppm) for 8 h

    Recommended WHO European Guidelines for Indoor Air Quality 2010[edit]

    7 mg/m3 (6 ppm) for 24 h (so as not to exceed 2% COHb for chronic exposure)


    Initial treatment for carbon monoxide poisoning is to immediately remove the person from the exposure without endangering further people. Those who are unconscious may require CPR on site.[29] Administering oxygen via non-rebreather mask shortens the half life of carbon monoxide to 80 minutes from 320 minutes on normal air.[21] Oxygen hastens the dissociation of carbon monoxide from carboxyhemoglobin, thus turning it back into hemoglobin.[6][92] Due to the possible severe effects in the fetus, pregnant women are treated with oxygen for longer periods of time than non-pregnant people.[93]

    Hyperbaric oxygen[edit]

    Hyperbaric oxygen is also used in the treatment of carbon monoxide poisoning, as it may hasten dissociation of CO from carboxyhemoglobin[6] and cytochrome oxidase[94] to a greater extent than normal oxygen. Hyperbaric oxygen at three times atmospheric pressure reduces the half life of carbon monoxide to 23 (~80/3 minutes) minutes, compared to 80 minutes for regular oxygen.[6] It may also enhance oxygen transport to the tissues by plasma, partially bypassing the normal transfer through hemoglobin.[92] However it is controversial whether hyperbaric oxygen actually offers any extra benefits over normal high flow oxygen, in terms of increased survival or improved long-term outcomes.[2][95][96][97][98][99] There have been randomized controlled trials in which the two treatment options have been compared;[100][101][102][103][104][105] of the six performed, four found hyperbaric oxygen improved outcome and two found no benefit for hyperbaric oxygen.[2] Some of these trials have been criticized for apparent flaws in their implementation.[106][107][108][109]A review of all the literature on carbon monoxide poisoning treatment concluded that the role of hyperbaric oxygen is unclear and the available evidence neither confirms nor denies a medically meaningful benefit. The authors suggested a large, well designed, externally audited, multicentre trial to compare normal oxygen with hyperbaric oxygen.[2]


    Further treatment for other complications such as seizure, hypotension, cardiac abnormalities, pulmonary edema, and acidosis may be required. Increased muscle activity and seizures should be treated with dantrolene or diazepam; diazepam should only be given with appropriate respiratory support.[29] Hypotension requires treatment with intravenous fluids; vasopressors may be required to treat myocardial depression.[110] Cardiac dysrhythmias are treated with standard advanced cardiac life support protocols.[17] If severe, metabolic acidosis is treated with sodium bicarbonate. Treatment with sodium bicarbonate is controversial as acidosis may increase tissue oxygen availability.[111] Treatment of acidosis may only need to consist of oxygen therapy.[17][22] The delayed development of neuropsychiatric impairment is one of the most serious complications of carbon monoxide poisoning. Brain damage is confirmed following MRI or CAT scans.[16][112][113] Extensive follow up and supportive treatment is often required for delayed neurological damage.[21] Outcomes are often difficult to predict following poisoning,[114] especially people who have symptoms of cardiac arrest, coma, metabolic acidosis, or have high carboxyhemoglobin levels.[22] One study reported that approximately 30% of people with severe carbon monoxide poisoning will have a fatal outcome.[55] It has been reported that electroconvulsive therapy (ECT) may increase the likelihood of delayed neuropsychiatric sequelae (DNS) after carbon monoxide (CO) poisoning.[115]


    The true number of incidents of carbon monoxide poisoning is unknown, since many non-lethal exposures go undetected.[16][55] From the available data, carbon monoxide poisoning is the most common cause of injury and death due to poisoning worldwide.[116] Poisoning is typically more common during the winter months.[7][117][118][119] This is due to increased domestic use of gas furnaces, gas or kerosene space heaters, and kitchen stoves during the winter months, which if faulty and/or used without adequate ventilation, may produce excessive carbon monoxide.[7][120] Carbon Monoxide detection and poisoning also increases during power outages.[121][122][123]

    It has been estimated that more than 40,000 people per year seek medical attention for carbon monoxide poisoning in the United States.[124] In many industrialized countries carbon monoxide is the cause of more than 50% of fatal poisonings.[3] In the United States, approximately 200 people die each year from carbon monoxide poisoning associated with home fuel-burning heating equipment.[83] Carbon monoxide poisoning contributes to the approximately 5613 smoke inhalation deaths each year in the United States.[125] The CDC reports, "Each year, more than 500 Americans die from unintentional carbon monoxide poisoning, and more than 2,000 commit suicide by intentionally poisoning themselves."[126] For the 10-year period from 1979 to 1988, 56,133 deaths from carbon monoxide poisoning occurred in the United States, with 25,889 of those being suicides, leaving 30,244 unintentional deaths.[125] A report from New Zealand showed that 206 people died from carbon monoxide poisoning in the years of 2001 and 2002. In total carbon monoxide poisoning was responsible for 43.9% of deaths by poisoning in that country.[127] In South Korea, 1,950 people had been poisoned by carbon monoxide with 254 deaths from 2001 through 2003.[128] A report from Jerusalem showed 3.53 per 100,000 people were poisoned annually from 2001 through 2006.[129] in Hubei, China, 218 deaths from poisoning were reported over a 10-year period with 16.5% being from carbon monoxide exposure.[130]k
  • VictoriaEnergy
    VictoriaEnergy Member Posts: 126
    Chimney Venting

     If you are going to switch to a masonry or metal chimney with this boiler, my advice would be to only do it if you can install the chimney inside the heated envelope of the house.  If you install an exposed chimney on this boiler you will run into more problems with condensation and corrosion in the chimney.

    One alternative you could look at would be a Tjernlund power vent system.  These have been around for quite a few years.  They work.  They are a bit noisy.
    Home Owners Please Note:

    You are receiving advice from some very skilled pros completely free of charge. One of the reasons I participate is to sharpen my own troubleshooting skills. So; did we get it right? I would be grateful if you extend this courtesy back by posting the final outcome of the issue you are inquiring about. Thanks
  • Steamhead
    Steamhead Member Posts: 16,841
    The short version:

    this thing's gonna kill you.

    Do NOT allow the installing company back in your house. Find someone who knows what they're doing and have them take over. Then take whatever action is needed to get your money back from Beavis and Butt-head, including repairing the damage to your siding. It might also be a good idea to put in a complaint to your local licensing authorities.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Gordy
    Gordy Member Posts: 9,546
    Long form CO

    Sorry for the long form, but sometimes a link just does not cut it. Dangerous stuff!
  • Rich_49
    Rich_49 Member Posts: 2,766
    Would also

    report the inspector who insisted on this device . Your state probably has a regulatory board for such things . Remember all , an inspector is NOT the authority having jurisdiction , he is just a man placed in a position to enforce the states adopted model code .  You and you alone as the licensed professional have a DUTY to disobey the inspector when and if he is wrong . Especially when peoples health and well being are at risk . DPB , I would have an attorney contact the town's attorney also . The original installer at this point should be held liable for all expenses incurred by you to correct this situation . Remember contractors , you must have and use the BALLS God gave you .  If you don't you may one day hear his honor say " Sir , you are a licensed contractor in this state , act like it ! Judgement for the plaintiff "
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Bob Harper
    Bob Harper Member Posts: 1,035
    get protected

    A CO detector or alarm listed to UL 2034 is junk that will not protect you against CO poisoning. It is designed to alert only once you have a carboxyhemoglobin level of 5%. If your alarms have alerted then by definition, you have already had CO poisoning.

    Get a pro in there who is NCI certified in CO. Also, you cannot vent under positive vent pressure unless the venting is listed to UL 1738. No homemade junk with joints gooped with red RTV silicone.

    Do Not operate this appliance until corrected.
  • vaporvac
    vaporvac Member Posts: 1,520
    edited November 2013
    Which Co protectors?

    This happens to be on today's shopping list. Are there any you would suggest? I'm unfamiliar with the different types. (Homeowner here.) Thank you.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • rick in Alaska
    rick in Alaska Member Posts: 1,457

    My last post got dumped somehow, so here is a shortened version of it.

    Find out if the boiler is really putting out that kind of co or not . Is the dryer gas?

    If the boiler is putting out that amount of co, get it fixed immediately. I never leave a boiler running more than 50ppm, but usually closer to 15.

    If you are getting back draft through the barometric on the air intake line ( damper is required up here not for draft, but in case vent gets blocked outside .But it must be set up right), then you have an air issue inside the house that is making the house negative pressure. I suspect you do not have enough combustion air in the basement to run the dryer and anything else that might be pulling air out.

    Although the exhaust vent does not look good, it is mostly an insulated chimney connector, and the joints are sealed ok. I doubt you are getting exhaust leakage through it. But a smoke bomb test in the boiler would prove any leakage.

    The exhaust termination is ok for that boiler, but according to a local rep here, i you were to cut a 3" hole through the center of it, it would direct the exhaust gases out further such as some direct vent water heaters do. This might help with any air being pulled back in through the air intake, such as on breezy days, and help with the staining on the wall caused by the acid in the exhaust gas hitting a cold wet wall.


    p.s. check the door seal on that boiler as I had one that the gasket was not sealing as it should.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Which Co2 protectors?

    "Are there any you would suggest?"

    I am a homeowner too. I read about these on this web site a couple of years ago, and I have the 2010, 2011 or so model.

    Strangely enough, they come with a long-life lithium 9-volt battery that lasts only about 3 months. A regular 9 volt battery lasts about a year. My theory about that is that the lithium ones cost a lot more, so they spend a long time on the shelves and in the warehouses, so by the time you buy one, their shelf life is almost over. So unless you can be sure you are getting fresh ones (and if you can, let me know how), use the regular ones and replace them every year.

  • Bob Harper
    Bob Harper Member Posts: 1,035
    CO not CO2

    CO2 is what you are exhaling. You want an unlisted low level CO monitor-not an alarm. There are currently only two I'm aware of available in the US:

    CO Experts

    NSI 3000

    The NSI is available only through certified contractors and they are currently backordered into Jan.

    George has raised the cost of the CO Experts recently so check his web site for pricing and discounts.

    NCI uses 100ppm as the max. an appliance can be emitting into the flue gases. They do not allow more than 30ppm in the room based upon various national stds.

    Listed CO alarms are designed to warn only against CO death--not just poisoning. The fact you had a CO alarm alert means you were poisoned. Most any fire marshal would red tag this installation and shut it down or force you out of this house.
  • vaporvac
    vaporvac Member Posts: 1,520
    Thanks for recommendations...

    I thought I'd edited that. Typo due to too much food. yes , co is what Imeant.
    Two-pipe Trane vaporvacuum system; 1466 edr
    Twinned, staged Slantfin TR50s piped into 4" header with Riello G400 burners; 240K lead, 200K lag Btus. Controlled by Taco Relay and Honeywell RTH6580WF
  • Jack
    Jack Member Posts: 1,047

    I remember when Tjernlund designed the SSII power venter. One of the original goals was to take it to manuf and let them test it to be used without a barometric for their particular systems. That idea ran right into the time when all those manuf said they didn't need a supplemental venter. They could do it all with the burner. Sometimes it works well, sometimes not. I guess like everything else.

    My suggestion to you is that you get a Buderus Rep in there with the technician. You are in MA and they have excellent representation there. Insist upon it. Make sure the guy coming out has his fast ball too and ask specifically for that "right guy" on this model boiler.

    If you decide to build a chimney for this I would strongly vote for a factory built chimney. Do not use masonry. Masonry chimneys are 11th century technology venting 21st century appliances. Use as small a chimney as you can get approved by the manuf, and your local code official. I bet 5" would be just fine on this.