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Old 06-03-2016, 09:18 PM   #1
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CO monitor false alarms

I own a diesel trawler (a DeFever 48) and failed the last safety inspection because I don't have CO alarms aboard (It didn't help to tell the inspector diesels don't emit CO).

Anyway, whenever the boat is closed up (and not operating) my CO alarms trigger within 24 hours; I have 3 aboard and all three go into alarm. There is no possible source of CO aboard and my batteries are in rest mode (not being charged).

Any ideas what other gasses cold be causing this? I have not done anything recently like painting or varnishing. Suggestions appreciated.

John
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Old 06-03-2016, 10:16 PM   #2
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So I have to preface this by saying that my experience is with terrestrial CO detectors. YMMV with anything stamped "marine."

Generally, CO detectors aren't set for a particular threshold level, they work on the idea of Time Weighted Average. The higher the concentration, the shorter exposure interval before alarm. They tend to have fewer false activations than both types of common household smoke detectors.

And I'm not sure who told you that Diesel engines do not produce CO, but they are dangerously mistaken. CO is a byproduct of incomplete combustion, and is present in diesel exhaust. Heck, I have to bump test our CO detectors at work on a weekly basis, and I do it by standing downwind of the diesel exhaust. They alarm at 25ppm, which I can get without even feeling the exhaust heat.

That being said, the detectors have a limited lifespan, generally accepted to be 10 years. We have a huge development in our city that started about 12 years ago, and they have monitored fire protection systems, including CO. For whatever reason, the CO detectors the builder installed all seem to die right at that 10 year mark, and those poor guys run at least one, sometimes more false positive CO alarms daily.

I'd suggest replacing the detectors, but leave the old ones in place for a bit. If the new ones alarm, you might have a CO problem. And it might not even be you. It might be an upwind neighbor. Gas engines produce a lot of CO, and I have seen idling cars near open windows trigger them before.

Good luck. I'm not sure about where you are, but here all the Fire Department apparatus carry calibrated CO monitors, and will come and sweep your home if you have an alarm or even just call.
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Old 06-03-2016, 11:34 PM   #3
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I had the same problem last week and finally traced it back to batteries off gassing. I used a cheap Arikon CO detector from Amazon that shows the PPM on the display to help me track down the source.

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Old 06-04-2016, 06:52 AM   #4
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I find one of my smoke detectors doesn't like high humidity...

But other than that, the dozens of home smoke and CO detectors I have had aboard 3 different liveaboards seem to work just fine. No false alarming, alarming for out gassing batteries, or slightly overdone galley "meals"....

If the boat was closed up with no one sboard, was the humidity high? Is there new anything onboard like carper, furniture, was coverings, etc that could be gassing?

As to CO alarms and their sensitivity...this was sent to me by a marine diesel generator engineering expert......concerning testing detectors in diesel engine exhaust. Forum tidbits can be misleading or misread by anyone so like all info....often crosschecking info is wise....

" .......most consumer grade detectors have a high cross sensitivity to both water vapor and oxides of nitrogen (NO and NOx) both of which are abundant in diesel exhaust. Maybe that has something to do with his alarm going off?

Not to mention that the 8 hour exposure limit in mines is 50ppm and few boaters sleep in the exhaust plume of their engines.

If this guy tests his workplace detectors by "standing downwind of the diesel exhaust" I suspect OSHA would have a field day at his workplace. There are very specific regulations for the testing of CO detectors in industrial workplaces and standing near a diesel exhaust pipe is not one of them. If those detectors are required at his workplace by regulation and are that sensitive then he has just admitted to a very serious violation."
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Old 06-06-2016, 08:16 AM   #5
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Thanks to all for your replies; problem solved. It appears that my battery charger did malfunction and it was charging my batteries continuously. Normally I can hear the fan running but apparently a nearby lightning strike must have taken out the circuitry and the fan as well; my batteries were continuously charging

Time to replace it. Finally I would like to correct my initial comment about CO emissions, what I should have said was that diesels do produce CO when running but almost 30 times less than gasoline engines therefore it is not really a significant threat.
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Old 06-06-2016, 03:42 PM   #6
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That was my experience as well. Xantrex battery charger, by chance? CO detectors seem to be good broken-charger-alarms.
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Old 06-06-2016, 04:39 PM   #7
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I had that problem the co2 alarm I read the back you have to use a pisific brand of battery I did that no more false alarms
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Old 06-06-2016, 04:48 PM   #8
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Not sure a detector warning me of gassing batteries is a false alarm....

Especially when that danger could be an explosion and or fire instead of the prescribed alert of something that may take hours to kill if at all.....before waking or noticing it.
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Old 06-06-2016, 07:31 PM   #9
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Quote:
Originally Posted by Pure pleasure View Post
I had that problem the co2 alarm I read the back you have to use a pisific brand of battery I did that no more false alarms
Say again !?!?!?
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Old 06-12-2016, 01:28 PM   #10
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That was my experience as well. Xantrex battery charger, by chance? CO detectors seem to be good broken-charger-alarms.

I also have had the same experience, $29.00 broken Xantrex battery charger alarm powered by 2 AA bats.

Xantrex is Latin for "Prince of Darkness"
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