CO2 Alarm

mcalan

mcalan

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Hi I'm currently out of the UK and away from my boat for about 8 weeks.
I received a text from my neighbour in the marina(they are a live a board) that there was a beeping coming from within. I telephoned the marina and one of the guys went down to investigate. They called me back and said "nothing to worry about" it was the C02 alarm, and they have removed the batteries.
He went on to say as the boat was closed up and it was hot the air would have been stale and that's what set it off, or it could have been the batteries gassing!
my question is do I need to worry
 
Why do you have a CO2 alarm on your boat?

Many boats have a CO alarm and/or a propane gas alarm.

I've not heard of a CO2 alarm before. :confused:
 
Some CO alarms are combined with a gas (lpg) detector. An lpg detector will be triggered by hydrogen, or any other flammable gas for that matter.

Check with the instructions/ manufacturers literature. Your CO detector might be sensitive to hydrogen. I'm not sure off hand if there is likely to be any cross sensitivity or not.

If due to hydrogen you need to investigate further. Leave the batteries off charge until you have checked out the charging.
 
VicS said:
Some CO alarms are combined with a gas (lpg) detector. An lpg detector will be triggered by hydrogen, or any other flammable gas for that matter.

Check with the instructions/ manufacturers literature. Your CO detector might be sensitive to hydrogen. I'm not sure off hand if there is likely to be any cross sensitivity or not.

If due to hydrogen you need to investigate further. Leave the batteries off charge until you have checked out the charging.
Click to expand...

An lpg detector shouldn't come into contact with hydrogen since it would be best positioned deep in the bottom of the boat, whilst the hydrogen will be sitting right at the deck head. It's possible that the CO alarm could detect it, but if there is any ventilation at all in the boat then the hydrogen should all escape before reaching the concentrations required to set an alarm off.
 
Woodlouse said:
An lpg detector shouldn't come into contact with hydrogen since it would be best positioned deep in the bottom of the boat, whilst the hydrogen will be sitting right at the deck head. It's possible that the CO alarm could detect it, but if there is any ventilation at all in the boat then the hydrogen should all escape before reaching the concentrations required to set an alarm off.
Click to expand...

Hydrogen is a very small molecule. It will diffuse quickly throughout the space into which it is released and certainly will not be sitting at the deck head. Remember the experiments you were shown in your junior science lessons to demonstrate this!
For the same reason, however, it will quickly escape.
 
mcalan said:
Its just a standard co alarm at head height above the chart table the boat is closed up with little ventilation at the moment as Im away
Click to expand...

I think you will find that electrochemical carbon monoxide detectors are sensitive to hydrogen! The degree of sensitivity varies I believe.
 
VicS said:
Hydrogen is a very small molecule. It will diffuse quickly throughout the space into which it is released and certainly will not be sitting at the deck head. Remember the experiments you were shown in your junior science lessons to demonstrate this!
For the same reason, however, it will quickly escape.
Click to expand...
It's a small molecule that is lighter than air though, so will generally diffuse in an upwards direction surely? I'm afraid H&S got to junior scientists playing with flammable gasses before I got there. Bunsen burners was about as exciting as it got for us.
 
Woodlouse said:
It's a small molecule that is lighter than air though, so will generally diffuse in an upwards direction surely? I'm afraid H&S got to junior scientists playing with flammable gasses before I got there. Bunsen burners was about as exciting as it got for us.
Click to expand...

No it will diffuse throughout the space ... a basic property of gases but hydrogen being so small does it quickly.

Standard demo is to fill a gas jar with hydrogen and stand it on top of another just containing air. Towards the end of the lesson both are tested with a lighted taper both explode with equal vigour. The kids can do it on a test tube scale as well but a gas jar full of hydrogen and air makes a more memorable bang.

Similar experiment with bromine vapour except that an empty jar is stood on top of one containing bromine vapour. Eventually the concentration of bromine can be seen to be the same in both jars despite the fact that bromine vapour is very much more dense than air. Not so impressive because it takes longer than a single lesson

Can do similar experiments to demonstrate diffusion in liquids as well.
 
VicS said:
No it will diffuse throughout the space ... a basic property of gases but hydrogen being so small does it quickly.

Standard demo is to fill a gas jar with hydrogen and stand it on top of another just containing air. Towards the end of the lesson both are tested with a lighted taper both explode with equal vigour. The kids can do it on a test tube scale as well but a gas jar full of hydrogen and air makes a more memorable bang.

Similar experiment with bromine vapour except that an empty jar is stood on top of one containing bromine vapour. Eventually the concentration of bromine can be seen to be the same in both jars despite the fact that bromine vapour is very much more dense than air. Not so impressive because it takes longer than a single lesson

Can do similar experiments to demonstrate diffusion in liquids as well.
Click to expand...

How does that relate to gasses such as propane and CO2 settling low down in a space then instead of mixing with the air? Or does it still happen, just at a much slower rate?
 
Woodlouse said:
How does that relate to gasses such as propane and CO2 settling low down in a space then instead of mixing with the air? Or does it still happen, just at a much slower rate?
Click to expand...

Initially propane, butane and CO2 tend to sink so low down is the best place for detectors. Eventually they will diffuse throughout the available space. In practice convection currents within the space may well speed up the process
 
The ( standard fit) wired in CO detector I had was very sensitive to voltage drop (it was connected to the 12v battery) and would beep at a regular interval if the voltage was only slightly down (a built in safety feature, I expect, to warn that it might not be getting the required voltage).

I replaced it with a stand alone battery powered unit ( which will also sound an alarm warning when it's battery gets low)
 
Sounds like a faulty alarm. Have had problems with these before. Incomplete combustion is what causes carbon monoxide so if everything is shut down (galley/engine/generators) then you shouldn't be getting carbon monoxide.
 
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