Jump to content

Carbon monoxide alarm

ian bell

Recommended Posts

Alarm went off after going to bed. Opened doors and windows. Alarm stopped and didn't reactivate. Gas cylinder not turned on all day but blown air central heating was on all day and evening. Habitation check done last November. Contacted the Council for Gas Detection and Environmental Monitoring helpline who suggested overcharging of leisure battery giving off hydrogen. Any ideas?


Link to comment
Share on other sites

Did you follow up their suggestion and check the venting on the battery (if it's unsealed) and check the charger is working correctly.


Was the fridge running on gas at the time, is it sealed properly from the interior of the van & when was the burner last checked..

Normally CO is only given off in harmful quantities if a gas flame is burning incorrectly tell tale sign is a yellow flame.

Link to comment
Share on other sites

Welcome to the Out&AboutLive forums, Ian.


A GOOGLE-search using "carbon monoxide detector false alarms" provides a fair amount of advice. For example




It's clearly very unwise in your case to assume your alarm was false. On the other hand, if no gas appliances (heater, fridge, cooker) had been in use shortly before the alarm went off (presumably your blown-air heating was 230V-powered), it's difficult to understand what caused it to activate.


There are on-line suggestions that high humidity in a room can result in a false alarm, that the alarms can 'spike' of their own accord and, of course, that alarms can develop faults.


A Canadian website carries this (1996) advice


"Carbon Monoxide Detectors and Charging of Lead Acid Batteries


When charging lead acid batteries, hydrogen (H2) gas is produced. Hydrogen gas is a by-product from the electrolysis reaction (charging) of the lead acid battery. Hydrogen gas can interfere with the carbon monoxide detector's sensor. The carbon monoxide sensor is sensitive to and will respond to hydrogen gas at about a 10 to 15 % of it's actual concentration. If you find you are getting high carbon monoxide readings around battery charging operations do not be alarmed, but be cautious. The Lower Explosive Limit (LEL) for hydrogen is 4.0 % by volume (40,000 ppm by volume). If your carbon monoxide detector alerts, and you are charging a lead acid battery in the area, disconnect the battery charger and ventilate the space in order to dissipate the gas.


The public should be aware of the limitations and interferences that can affect CO detectors. CO detectors are electrochemical sensors, which detect a variety of specific gases. In most cases, the gas of interest reacts with the chemical solution in the sensing electrode to produce ions (charged particles) that move through the solution to an electron-accepting electrode, completing an electric circuit. The number of ions produced and the magnitude of the current developed are proportional to the concentration of the gas being measured.


Additional interfering gases of similar molecular size and chemical reactivity may produce false positive response. Major interferents that can affect CO detectors are acetylene, dimethyl sulfide, ethyl alcohol, ethylene, hydrogen cyanide, hydrogen sulfide, isopropyl alcohol, mercaptan, methyl alcohol, propane, nitrogen dioxide, and sulfur dioxide."


So the CoGDEM's suggestion cannot be discounted. Having said that, if your leisure-battery had been 'gassing' there's no good reason to expect it to stop. If gassing had caused the alarm to sound in the first place, one might reasonably expect the alarm to go off again once you had shut the doors and windows.


As your alarm has not gone off again, if a thorough check of your motorhome reveals no credible explanation I think you'll have to assume that either it was a one-off false alarm or your alarm is faulty. In both cases (as is suggested on some other websites) all you can really do is fit another alarm - perhaps a higher specification one like a Kidde 10LLDCO (assuming that's suitable for vehicles) that provides a data readout - and see if that one goes off too.

Link to comment
Share on other sites

Have been using CO alarms in campervans for about 15 years, several times the alarm has gone off when the van has been left for long period without use in winter, this is presumably due to cold/damp, so now remove batteries during winter months if the vans not being used. Doesn't sound like the cause of your alarm but worth bearing in mind.

The alarm in my mothers house has decided to occasionally go off, all appliances have been checked and no faults, I installed a second alarm with screen and this shows no trace of CO even when the first goes to alarm, so in this case the alarm seems to have developed a fault.

As per Derek's post, have you checked the battery for gassing?

p.s. in my experience CO alarms are very sensitive to exhaust fumes, could it have been a vehicle close by with engine running?


Link to comment
Share on other sites

  • 2 months later...

Thanks to you all for replying.

I checked the battery charging rate and it was ok. Sealed battery so no venting required. I had a full co check done by my mobile service engineer after simulating the original circumstances ( blown air heating on, curtains and blinds closed etc). Tested ok. Rang the helpdesk at the alarm manufacturer, Kidde, and was told that it was most probably a false alarm due to condensation as the van had stood all winter and then heated up inside. They recommended I removed the alarm whenever I was not using the van and keep it in the house until needed again. We have had several trips in similar circumstances since the original incident without any problems, so I am going with that theory until proved otherwise. To be on the safe side I have fitted another alarm.

Colin's post hinted at this so it seems plausible,


Ian Bell.

Link to comment
Share on other sites

" Sealed battery so no venting required"


And here possibly lies your problem. No battery is actually 100% sealed. A gel or AGM are 'sealed' with one way pressure relief valves. As they get older and gasses are not recombined properly then the valves will release the excess gas.

In wet flooded batteries 'sealed' means sealed against mantentance NOT sealed against venting.


All batteries should be located in a well ventilated area, and if possible vented through a tube to the outside world. You should never fit a 'sealed' flooded battery which has no provision for a vent tube to be attached inside your vehicle but only in an exterenal well ventilated locker.


I would check your sealed battery as it may well have the provision for a vent tube to be fitted.


Of course your alarm could also have triggered because of heater exhaust fumes entering the vehicle as well, but the battery issue needs to be addressed.

Link to comment
Share on other sites

  • 2 weeks later...


This topic is now archived and is closed to further replies.

  • Create New...