source of carbon monoxide...what is source

[JAU]

At 2 am our carbon monoxide detector went off. We are in our marina at Herring Bay/Chesapeake. We are connected to shore power have both air conditioners on, normal things. Jeanneau 2007 45 SO. So unit is 18 months old so opened all hatches, changed battery and went back to bed about an hour later. Week later 4 am goes off again, so open hatches thinking the unit is failing, same situation, hot outside humid outside, but air condition makes cabin very comfortable. This weekend bought a new unit, it goes off! Open hatches ...what could be the source, we are don't have our diesel engine on, only new thing is we've updated our inverter to a newer unit, Freedom. There are motor boats around us, but in middle of night?

[john61ct]

Does it also detect fuel, other hydrocarbons?

[geoleo]

Originally Posted by JAU

At 2 am our carbon monoxide detector went off. We are in our marina at Herring Bay/Chesapeake. We are connected to shore power have both air conditioners on, normal things. Jeanneau 2007 45 SO. So unit is 18 months old so opened all hatches, changed battery and went back to bed about an hour later. Week later 4 am goes off again, so open hatches thinking the unit is failing, same situation, hot outside humid outside, but air condition makes cabin very comfortable. This weekend bought a new unit, it goes off! Open hatches ...what could be the source, we are don't have our diesel engine on, only new thing is we've updated our inverter to a newer unit, Freedom. There are motor boats around us, but in middle of night?

It is the hydrogen gas coming from the batteriesm as they are being charged

[GordMay]

Greetings and welcome aboard the CF, JAU.

Carbon monoxide alarms only go into alarm when they detect CO (either from your boat, or another nearby source). In addition to this, some cheap carbon monoxide detectors can be set off by Hydrogen gas, and some even claim that large quantities of petrol fumes can trigger false alarms.
Unlike smoke alarms, where dust, cooking fumes, high humidity, etc. can cause false alarms; the same problem does not exist with CO alarms.
That’s because CO alarms work very differently from smoke alarms.
When CO is present, it enters the sensor through a gas diffusion hole. A graphite filter prevents any external contaminants from entering. A Platinum sensing electrode then catalyses the oxidation of the CO. Combined with the water present in the electrolyte, this reaction causes the voltage to rise and consequently, a small current flows between the two electrodes. This output is directly proportionate to the amount of CO gas present. The microchip in the unit then activates the LED/horn/display to give a warning applicable to the CO level sensed.
As you can see, it's a complicated process, which is why CO alarms are considerably more expensive than smoke alarms, and also why they very rarely go into false alarm. In fact, the only reason for them to false alarm is not from external contamination, but if there is something wrong with the alarm itself. If you get a good quality CO alarm from a reputable manufacturer, then this should never be a problem.

My advice is to discover the source of CO (or perhaps Hydrogen gas (H2), or get a better detector.

[landsend]

Our CO alarm goes off when boats pass by close while we are at anchor. They are very sensitive. At 2 am? Very avid fishermen?

[JAU]

thank you, going to get a better detector and also pursue hydrogen gas option, thinking we have two batteries in bow that could be putting off gas in same area of detector, all of our other batteries are in stern and are cells...

[bobgarrett]

We had a similar problem and a shirt while later a battery failed getting very hot. Problem solved by initially disconnecting the battery and then removed from boat and replaced.
A search if the internet showed this CO warning for a failing battery is common.

[wrwakefield]

Our old CO alarms [commercial combination smoke and CO] would sometimes sound a false-positive alarm about 3 hours into equalizing our FLA house battery bank from errant hydrogen escaping the ventilated battery compartment. [Even though the battery locker and boat are both well ventilated.]

In 2018 we upgraded with Nest Smoke/CO alarms- 2nd gen [for other reasons as well] and only have had one false alarm in a year [we are aboard full time] when the engine bank was inadvertantly combined during a house equalization cycle...

Consider Nest if you have full time WiFi [local] on your vessel. The 4 detectors we have in different cabins stay interconnected that way, and if one has an alert, it is broadcast over all the others- an excellent safety enhancement for us.

e.g., "Heads up; the forward cabin is getting smokey. The alarm may sound..."

"The smoke in the forward cabin is getting worse... [or better...]"

They also announce whether the situation is getting worse or better... [After opening a hatch after burning the toast, for instance...]

There are also many other features we find worthwhile including remote notification on to our phones.

In case this is useful.

Cheers! Bill

[S/V Illusion]

Most CO monitors will detect hydrogen gas emitted from improperly charging batteries. As someone else suggested, that is your likely problem and a good warning to check your charging system and the possibility of a ‘bad’ or dying battery

[geoff3nebel]

So many others have mentioned it, but I'll add my two pennyworth: it's almost certainly your batteries.
I have three monoxide detectors and it's always at night when I'm asleep when the damn things go off one after the other...

[Hardhead]

Originally Posted by GordMay

Greetings and welcome aboard the CF, JAU.

Carbon monoxide alarms only go into alarm when they detect CO (either from your boat, or another nearby source). In addition to this, some cheap carbon monoxide detectors can be set off by Hydrogen gas, and some even claim that large quantities of petrol fumes can trigger false alarms.
Unlike smoke alarms, where dust, cooking fumes, high humidity, etc. can cause false alarms; the same problem does not exist with CO alarms.
That’s because CO alarms work very differently from smoke alarms.
When CO is present, it enters the sensor through a gas diffusion hole. A graphite filter prevents any external contaminants from entering. A Platinum sensing electrode then catalyses the oxidation of the CO. Combined with the water present in the electrolyte, this reaction causes the voltage to rise and consequently, a small current flows between the two electrodes. This output is directly proportionate to the amount of CO gas present. The microchip in the unit then activates the LED/horn/display to give a warning applicable to the CO level sensed.
As you can see, it's a complicated process, which is why CO alarms are considerably more expensive than smoke alarms, and also why they very rarely go into false alarm. In fact, the only reason for them to false alarm is not from external contamination, but if there is something wrong with the alarm itself. If you get a good quality CO alarm from a reputable manufacturer, then this should never be a problem.

My advice is to discover the source of CO (or perhaps Hydrogen gas (H2), or get a better detector.

Great post - learn something everyday.

[AKA-None]

Originally Posted by S/V Illusion

Most CO monitors will detect hydrogen gas emitted from improperly charging batteries. As someone else suggested, that is your likely problem and a good warning to check your charging system and the possibility of a ‘bad’ or dying battery

This feature just saved me when two separate ups’s had bad new batteries installed. Triggered before I could smell the hydrogen sulfide

[Midnight Son]

Originally Posted by S/V Illusion

Most CO monitors will detect hydrogen gas emitted from improperly charging batteries. As someone else suggested, that is your likely problem and a good warning to check your charging system and the possibility of a ‘bad’ or dying battery

FLA batteries when charged at maximum, start gassing H2 and Oxygen. Only really expensive CO sensors can be obtained that aren't cross sensitive to H2, for industrial gas monitors, ~$350.00, just for the sensor, monitor it goes in extra, unless you work in the mining/oil/chemical industries, and can get a corporate discount.

So false alarms will happen.

I and another member have responded to other threads of a similar bent, in the past.

[john61ct]

And offgassing FLA is required for healthy charging, nothing improper about it.

[Akapeterc]

One of our 2 year old, full river AGM batteries dropped a cell and started overheating and producing gas which was setting off our alarms until I discovered the problem I didn’t know what it was until I came home one day and the batteries were so hot close to exploding