Strange CO problem

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.

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.

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.

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.

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.

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.

Does CO2 give a false

reading to a CO detector?  I heard that it did...