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Strange CO problem

Working on a oil boiler in a basement today.  Shut the boiler off to drain two zones. Started to solider for about 5 minutes about 25' away from a CO detector (outside the boiler room). The CO detector goes off, fire/police show up because of central station.

Fire department chief comes down to the basement with his portable CO detector and the CO starts to rise to about 70ppm. Fireman comes down with a little better unit and his is reading 50ppm and rising, tops off about 65ppm. I open a window to vent out the basement. Homeowner calls oil tech to come take a look. I get my Fyrite pro about an hour later to see whats going on.

My fyrite reads about 14ppm after 2hrs from the fire department came. Meanwhile the boiler been off the whole time. I fire the boiler with my fyrite close by, it never gets above 14ppm.

Oil tech comes in checks the draft in the flue and chamber, draft is very good at both points. No attic fans on on a/c on and nothing else on in the house.

Does anybody have clue what it could have been. I'm stumped


  • northernboiler
    northernboiler Member Posts: 55
    Probably just the soldering

    We ran into this issue one before. It was most likely due to the smoking caused if you clean the sweat joint with flux after soldering them. Or just by soldering the pipes alone, some fluxes can put off more smoke than others, that we have seen.

    The smoke from the soldering is or can get fairly thick and remain or hang depending on how the basement is.

    More to the point, now we make sure the room or area is well vented before we do any soldering or we temporarily disconnect the smoke/c02 detector until we finish.
  • Mpj
    Mpj Member Posts: 109

    I don't think that was the problem but is possible. After a couple of hours, I was soldering in the boiler room with the CO detector on the other side of the wall even long and it did not go off. The basement does not have any air flow to speak of and one tiny window.

    I guess I'll go with that.

  • icesailor
    icesailor Member Posts: 7,265
    CO and Smoke:

    If you are using a MAPP or Propane flame thrower to solder, it could have been CO. If it is a Air Acetylene "B" tank, it is the smoke and gas. I only use my "B" tank for soldering and I always check for a smoke detector before lighting up. I suffer from a rapid loss of serenity when they go off. I have accounts that have dedicated systems where I call the fire department to come and pull the box until I am done.

    You need to buy a personal CO detector like a UGI CO75 so that you will always know. You never know where you will find the silent but deadly killer. I found it on a hotel I stayed on  the way to Florida in Rocky Mount, NC. They didn't believe me and it is still there. It is as accurate as my Bacharach Fyerite Insight when put side by side on an exhaust.
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    CO & Soldering

    I havre several news stories where plumbers soldering in a building caused enough CO to make CO alarms go off.  I also know that welding upt out a high amount of CO.  Have received phone calls from our customers who have set off our low level monitor while soldering or brazing.  It is not unusual.
  • Bob Harper
    Bob Harper Member Posts: 977
    false alarms with listed CO alarms

    The GRI study back in 2002 noted a very high incidence rate of false alarms and cross-sensitivity to other gases, esp. aliphatic hydrocarbons. If your CO alarm does not have a carbon filter and is a MOS type 1 or type 2 sensor, it probably is very unreliable and susceptible to false positives. Electro-chemical sensors are generally very reliable and not sensitive to false positives or alerts.

    Before the NCI course, I had a Kidde Nighthawk with the digital display that would always spike in the 200-400ppm range on the display right after my wife used hairspray.

    Central station monitored CO alarms listed to UL 2075 are designed to meet the same parameters as battery powered single point alarms listed to UL 2034, which do not alert until you already have CO poisoning (or it thinks you do). They are designed to alert at 10% COHb, which is the definition of CO poisoning according to most agencies and even though 5% is considered an action level warranting medical treatment. The first symptoms of CO exposure such as headaches typically don't manifest until a COHb of about 15%. Therefore, symptoms of CO exposure are LATE signs and require immediate medical evaluation.

    Note that the GRI study found major problems with most listed alarms when the humidity was low. This effect started at about 50%Rh but got severe at 5%.

    Since you had a combustion-related operation going, your work could have produced CO or it could have been a false positive. No way of knowing. The recommendation is not to place CO alarms closer than 25LF from a combustion source. However, when working with a torch, it may be prudent to temporarily turn off the alarm by calling the central reporting station, advise them of the work ongoing and ask them to call your cell phone if you have not called them back by a fixed time before leaving the premises unguarded. Then, hang a sign and hang your truck keys on the sign.

    Always wear a personal CO alarm. As an alternative, you could place a portable low level CO monitor in the work area. This will respond within 60 seconds and is highly reliable without false positives.
  • Mpj
    Mpj Member Posts: 109

    I went back to the house today to finish some work. I was curious about my B tank making co,so I tested it with the Fyrite. I help the probe about five inches away and I got it up to about 20ppm.

    Anyway I went into the basement with the Fyrite and got 0 ppm. I did allot more soldering in the basement and the Fyrite never went above 0ppm. I can't figure it out.

    I will invest in a personal detector
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    CO False positive

    Bob, I wasn't sure if you were joking or not.  Most things with possibly the exception of nitrous oxide that cause CO Alarms to go off are usually toxic, explosive and sometimes flammable, such as hydrogen sulfide from lead acid batteries charging. Heavy duty cleaning compounds that contain methylene chloride can set them off.    Methylene chloride converts to CO in humans and does cause poisoning.

    If you have only one alarm in your house it should be near the sleeping area.  However if I have additonal alarms I want one in the kitchen if I have an unvented gas range, or in the family room if there is a fireplace(wood, gas etc) vented or unvented.  If I have a finished basement or a laundry room close to equipment I want an alarm there also.  70ppm after 1 hour anywhere near equipment is a problem.  But again, if you only have one, it should be near the slepping quarters.

    The 25LF recommendation is for responders who would rather they don't go off.
  • Mpj
    Mpj Member Posts: 109


    Would my Acetylene tank set off the alarm if it was leaking?
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    Leaking Acetylene

    Yes I have had my customer and students call and say their personal CO monitors went off in their truck and they found leaking tanks. acetylene, propane.
  • Bob Harper
    Bob Harper Member Posts: 977
    LOL Jim

    When I referred to the 25LF, that was quoting the listed alarm installation instructions--not my recommendation. I agree with your 15LF from sleeping rooms and one per floor including the boiler room. As with that old case "Suicide in Sendai" you can have high levels in the basement, zilch throughout the building except the top floor where the stack effect and/ or mechanical ventilation carries it and it concentrates. I'd rather know its entering the room air right where it happens than wait for it to concentrate hopefully where I have a gizmo to detect it. I'd also rather have my personal alarm alert me to combustible gas leaking in my truck that's about to blow me up.

    A new threat is remote car ignitions with attached garages. Whether on purpose or by accident, this represents a very real threat to building occupants. We just had 4 killed in Pa last week by a car running in an enclosed garage. Still trying to get details on that one, whether suicide or accidental.

    The message I am getting out about the failings of UL listed CO alarms, whether 2034 single station battery powered store bought alarms or the 2075 central station monitored ones is the alert levels programmed are designed to protect only against CO death and not against CO poisoning. Let that soak in--not only do they fail at protecting against CO poisoning but they are not designed to! The listing plans on you being poisoned to a COHb of at least 10% before it is designed to alert. Gee thanks. That of course ASSumes the alarm is reliable and works as designed, which we know they generally don't. The public has been mislead about these devices.
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    Garage CO

    That was now an apparent domestic quarrel and the husband barricaded himself in the garage.  They say the family died trying to save him.  Their attempts were unsuccessful.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    the failings of UL listed CO alarms

    I share your concerns. Someone here (probably Tim McElwain) suggested one of these, that I now have. I have two big-box store CO detectors as well, but this one is right in my bedroom: Mine is a slightly older model.


    Here is an interesting video. People here already know it, but it is interesting anyway.

  • KCA_2
    KCA_2 Member Posts: 308
    Does CO2 give a false

    reading to a CO detector?  I heard that it did...
    :-) Ken
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    CO/CO2 interference

    CO2 will not cause a false CO alarm but instead it will prevent it by blocking CO from getting to it.
This discussion has been closed.