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evbeck · 13-05-2016, 08:28

After a four and nine-hour run under power, we shut down diesel, cleaned the boat and then stepped off for dinner. Engine shut off for three hours with boat open before we left. AC turned on forward, midship and aft. When we returned to closed up boat, the CO monitors mid and aft were going off and showed 40 and 39 levels of CO. We opened boat and waited and levels went down. Last night, closed boat to sleep with AC units on and the same CO monitors went off at 11:30 pm. Monitors not going off during or well after the diesel is shut off. Could this be hydrogen gas from batteries mixing with AC intake air? If so, it seems like the monitors would continue going off while AC running. thanks for any help.

**a64pilot** · 13-05-2016, 09:15

I'd say bad monitor, affected by moisture etc.
Except you had two fail, twice and at the same time? Odds against that are astronomical, so it seems you have CO somehow, stove on, maybe somebody close by running an engine or something.
I doubt hydrogen, reason is it is so light that if there is any, it's up there at the top of the boat, and CO detectors are located low in the boat?

I'd have to believe them and be cautious as CO is cumulative, it does not clear out of your body shortly with fresh air. But I have no idea why they are going off.

rwidman · 13-05-2016, 09:29

My first question would be; Are they connected together or independent?

CO detectors do not last forever, they "expire" and must be recalibrated at the factory or replaced. Some have an "end of life" signal. It's unlikely that two would expire at the same time but if they are connected together, it's possible that they would both alarm.

The manufacturer could answer your question about the hydrogen gas. They could probably help you determine why the detectors are alarming as well.

jeepbluetj · 13-05-2016, 09:32

I've had mine go off in the marina because a large powerboat across the fairway from me was running their engines for quite awhile. I opened up my boat and set a fan - (and spent the next 15 min or so off the boat)

evbeck · 13-05-2016, 12:36

Monitors are new and separate - one forward, one midship and one aft. Very odd because they don't go off when engine running or just after engine is run; we only used gas stove early in the morning, and no other boats running engines around us. Engine off today and monitors fine. thanks for responses.

sailjumanji · 13-05-2016, 15:12

Mine do off when cleaning with Mr Clean Multisurface cleaner. Both sensors do it. You said you cleaned the boat?

DRS · 13-05-2016, 15:27

I have had one go off on my boat when the regulator on the alternator failed and I cooked a battery to the point that it spilled out of the case. May want to check the charging system. Obviously not the alternator with the engines shut off but you did not say if you were on shore power although I suspect so with the AC on

just my 2 cents

Denman180 · 14-05-2016, 08:06

I think you are right about the gas from the batteries I had the same problem with a bad charger cooking one of my batteries. I replaced the battery and charger and the problem went away.

Robin3 · 14-05-2016, 08:09

I just had one, Kidde household type, go off for no reason when we were not on board but were plugged in and charging but on float at13v 0A checked the monitor and it was 15 years old and way beyond it' stated expiry date of 4 years ago. Bought new one and took the old on home, put in new batteries and it seems OK again. Confusing, you betcha.

wrwakefield · 14-05-2016, 09:13

Quote:

Originally Posted by evbeck

After a four and nine-hour run under power, we shut down diesel, cleaned the boat and then stepped off for dinner. Engine shut off for three hours with boat open before we left. AC turned on forward, midship and aft. When we returned to closed up boat, the CO monitors mid and aft were going off and showed 40 and 39 levels of CO. We opened boat and waited and levels went down. Last night, closed boat to sleep with AC units on and the same CO monitors went off at 11:30 pm. Monitors not going off during or well after the diesel is shut off. Could this be hydrogen gas from batteries mixing with AC intake air? If so, it seems like the monitors would continue going off while AC running. thanks for any help.

As you know, current CO sensors age out in 5 years time, and have a shelf-life date stamped on them somewhere visible [i.e., the unit does not need to be disassembled to find the date- at least in the US...] They are unreliable as they approach their expiration date.

The CO monitor in the cabin with our FLA battery bank [which is in a closed, externally vented locker] was triggered once while I was equalizing the batteries. [I had the battery locker open so the normal exterior venting was bypassed, but a port was open in that cabin...] Therefore, hydrogen gas was the culprit. When I closed the locker so the gas vented outside to boat, the CO alarm ceased even though the batteries were still in the equalization cycle...

You can generate hydrogen gas by putting a small amount of aluminum foil in dilute sodium hydroxide solution [e.g., drain cleaner dissolved in water...] to test your CO alarms with hydrogen gas... Remember when mixed with oxygen, hydrogen is flammable... [And that combo is explosive when in a sealed container...]

Certain spray cleaners also seem to trigger false CO alarms, but we haven't isolated which ones are the culprit yet... [An unrelated example: we have determined that Lysol spray- among others- will sometimes trigger a false alarm in our propane sniffer...]

Best wishes resolving this issue which cannot be ignored...

Cheers!

Bill

boatpoker · 14-05-2016, 09:35

Kudos Evbeck for taking this seriously. 8 out of 10 CO detectors I see on boats that I survey have the batteries pulled or wires cut because "the damn thing kept going off".

The symptoms of seasickness are dangerously similar to CO poisoning. It does not have to be fatal but small amounts of CO over a long period can cause brain damage of varying degrees due to reduced oxygen levels. It's wise to take the issue seriously.

Robin3 · 14-05-2016, 11:40

JUst got back from our boat and our new monitor was going. It has a digital display showing max level of 114ppm. Have it home right now and it is fine. We have a charger running 24/7 but it is in float mode showing 13.0v and 0A on both battery banks. Engine has not been run for a week and the cook stove not used at all for months. We did have someone working below a week ago who probably used a solvent cleaner to clean up. It is also very humid today like 93%. The boat was shut up completely, no hatches or vents open to allow exhaust gas from a neighbouring boat to get in. I fail to see where this thing is getting it's source and can really understand owners who just remove the things. Since we have no source of CO ( engine is diesel, we have no heaters) on board so really WTF is going on?? The unit in our case is new with a manufacture date of Jan 2016 and 10 year expiry on the sensor, it says. The monitor batteries are brand new too. I have never had a CO monitor on all my previous boats over 50 years so not sure of the need now.

wrwakefield · 14-05-2016, 11:52

Robin, At this point I would be suspect of the monitor(s)...
I standardized on these Kidde combo smoke and CO detectors, and like the talking feature - especially when guests are on board...

We haven't had one give false alarms yet- except for the battery equalization cycle event I mentioned in my earlier post...

For US$25 you could verify whether it is a false alarm or not... and one can always use another detector somewhere...

Thanks for mentioning the 10 year date- I didn't know there were some longer dated units on the market. I have only seen 5 year units.

Best wishes resolving the issue.

Cheers!

Bill