Rudely awoken- Carbon monoxide alarm

[Irob]

Interesting. But i still get confused by heavy fumes and light fumes. My co alarm is at mid height above my radiator in the bedroom, about 2 feet from my sleeping face, i feel thats the compromise position to collect heavy or light gases. Of course light gases will vent away through the mushroom vents and pidgeon house. If the heavies accumilating low down are dangerous then the alarm should be near the floor at the lowest part of the boat. But i,ve a feeling the installation instructions usually say mount them up high. I,m confused.

[WotEver]

5 hours ago, Irob said:

the installation instructions usually say mount them up high.

Yes, because CO is lighter than air. 

[Momac]

17 minutes ago, WotEver said:

Yes, because CO is lighter than air. 

No its not. It is much the same.

Carbon monoxide is real risk on boats . 

I am surprised the BSS does not require a CO alarm.

Switching the alarm off is , in my opinion, not a wise decision . If the alarm sounds the cause should be investigated.

[WotEver]

35 minutes ago, MartynG said:

No its not. It is much the same.

However it is generally generated by incomplete combustion from a heating device which will also make it warm, which along with its slightly lower molecular weight helps it to rise towards the high level fixed ventilation. 

In a sealed environment (which a boat shouldn’t be, of course), it will tend to evenly disperse  

Agreed that CO alarms should be compulsory. 

[nicknorman]

6 hours ago, Irob said:

Interesting. But i still get confused by heavy fumes and light fumes. My co alarm is at mid height above my radiator in the bedroom, about 2 feet from my sleeping face, i feel thats the compromise position to collect heavy or light gases. Of course light gases will vent away through the mushroom vents and pidgeon house. If the heavies accumilating low down are dangerous then the alarm should be near the floor at the lowest part of the boat. But i,ve a feeling the installation instructions usually say mount them up high. I,m confused.

You can work out whether a gas is heavy or light by looking at its molecular weight. Air is mostly nitrogen which has an atomic weight of 14 but exists as a molecule N2 so has molecular weight 28. Carbon is 12, oxygen is 16 so CO also has a molecular weight of 28. So although I said CO is light, it is no lighter than air but it will tend to diffuse away and disperse readily. Compare with Propane, C3H8 molecular weight 44, much heavier than air.

[WotEver]

Air has a molar mass closer to 29, so is slightly ‘heavier’ than CO. 

Interestingly, H2O has a molar weight of only 18.

Edited January 5, 2018 by WotEver

[nicknorman]

14 minutes ago, WotEver said:

Air has a molar mass closer to 29, so is slightly ‘heavier’ than CO. 

Interestingly, H2O has a molar weight of only 18.

But of course due to diffusion, “brownian motion” if you like, gasses of different molecular weights tend to remain mixed to a large degree. It’s not like having liquids of differing densities such as oil and water.

[MtB]

17 minutes ago, WotEver said:

Air has a molar mass closer to 29, so is slightly ‘heavier’ than CO. 

Interestingly, H2O has a molar weight of only 18.

 

Oh so THAT'S why I get condensation on the underside of my steel slide hatches!

[WotEver]

18 minutes ago, Mike the Boilerman said:

Oh so THAT'S why I get condensation on the underside of my steel slide hatches!

You jest but I was wondering if it might actually have any relevance. Probably not. 

[nicknorman]

9 minutes ago, WotEver said:

You jest but I was wondering if it might actually have any relevance. Probably not. 

Not. It’s just that it isn’t insulated!

[alan_fincher]

4 hours ago, MartynG said:

Switching the alarm off is , in my opinion, not a wise decision . If the alarm sounds the cause should be investigated.

This ignores the fact that by far the most likely reasons an alarm will start to sound in an unoccupied boat with everything turned off, is either because it has gone low battery or reached the expiry date of the sensor.

This intensively annoying for those who are near the boat, and if they don't hold keys to it can only be resolved by fetching the owners, (maybe from many miles away), or by breaking in to silence it, (which I have known to happen).

What is likely to fill an unoccupied boat with CO?  Very little, I suggest.

[BruceinSanity]

1 hour ago, alan_fincher said:

This ignores the fact that by far the most likely reasons an alarm will start to sound in an unoccupied boat with everything turned off, is either because it has gone low battery or reached the expiry date of the sensor.

This intensively annoying for those who are near the boat, and if they don't hold keys to it can only be resolved by fetching the owners, (maybe from many miles away), or by breaking in to silence it, (which I have known to happen).

What is likely to fill an unoccupied boat with CO?  Very little, I suggest.

This^^^

With SA on a shoreline at the moment, I've left an ionising smoke alarm (to warn of overheating in the electrics cupboard) and a CO alarm (to warn of gassing batteries) active in the engine room, but removed the smoke alarm in the cabin, which gets cold and a bit damp in the unheated boat and starts chirping. In the past, I've taken out the CO alarm in the cabin too, but it seems to be behaving itself this winter.

Needless to say, all alarms are reactivated if anyone is sleeping on the boat.

[Irob]

I,m glad many are as confused as i am !   I like ventilation, makes me feel safe.  I think i,ll buy co alarms in bulk and put them everywhere.   If the low battery alarms sound then my neighbours will just have to tow her out into the cut and dump her !   Maybe we could tune the alarms to play music, like 'Smoke on the water ', or Authur Browns  'Fire '.  More environmentally friendly.

[rusty69]

7 hours ago, Irob said:

I,m glad many are as confused as i am !   I like ventilation, makes me feel safe.  I think i,ll buy co alarms in bulk and put them everywhere.   If the low battery alarms sound then my neighbours will just have to tow her out into the cut and dump her !   Maybe we could tune the alarms to play music, like 'Smoke on the water ', or Authur Browns  'Fire '.  More environmentally friendly.

Tempted to do that with our neighbours boat, whose alarm was sounding for three days over the Christmas period whilst they are abroad somewhere. 

I always take the batteries out of ours when away overnight. 

[Irob]

I suppose one could knit a wooly muffler to put over the blasted thing. Like covering the parrot.!

[rusty69]

2 minutes ago, Irob said:

I suppose one could knit a wooly muffler to put over the blasted thing. Like covering the parrot.!

That would be one big muffler, its a 60ft boat. Still, if I get knitting know, it might be ready for next Winter

[MtB]

On 05/01/2018 at 12:00, alan_fincher said:

This ignores the fact that by far the most likely reasons an alarm will start to sound in an unoccupied boat with everything turned off, is either because it has gone low battery or reached the expiry date of the sensor.

This intensively annoying for those who are near the boat, and if they don't hold keys to it can only be resolved by fetching the owners, (maybe from many miles away), or by breaking in to silence it, (which I have known to happen).

What is likely to fill an unoccupied boat with CO?  Very little, I suggest.

 

The opposing argument is is people switch off their CO monitors when leaving the boat, how likely are they to remember to switch them back ON again when they come back? 

[rusty69]

5 minutes ago, Mike the Boilerman said:

 

The opposing argument is is people switch off their CO monitors when leaving the boat, how likely are they to remember to switch them back ON again when they come back? 

Those with a checklist for arrival /departure should be ok.

[MtB]

Just now, rusty69 said:

Those with a checklist for arrival /departure should be ok.

 

And those without, condemned to certain DEATH.

Serves them right. 

[rusty69]

6 minutes ago, Mike the Boilerman said:

 

And those without, condemned to certain DEATH.

Serves them right. 

mmmmm, condemned to death, or spend two minutes writing out a checklist. Tricky one, I will have to give it further consideration.

[NB Lola]

I have my checklist on my phone in notes.

[alan_fincher]

2 hours ago, Mike the Boilerman said:

 

The opposing argument is is people switch off their CO monitors when leaving the boat, how likely are they to remember to switch them back ON again when they come back? 

Those I have been able to disarm, (whether smoke or CO) either result in the thing hanging down so you clump your head on it if you don't re-arm it on arrival back, or mean that they are completely removed from some kind of "arming" base.  If I place them somewhere inconvenient, (like on the main table), it's not hard to see they need putting back.

I must admit that the types that Nick described that you just insert a small bridge of wire in to disarm, but which could otherwise be left in place might need more rigour about re-arming them each time.  Generally though I think you can take them off the mounts like many other types - although perhaps not always easily so.

[Chewbacka]

6 hours ago, Mike the Boilerman said:

 

And those without, condemned to certain DEATH.

Serves them right. 

Not quite, as you would also need a source of CO at a fatal level which I have never had.  However I do have a couple of CO alarms.

The one's with replaceable batteries have them removed when I leave the boat for more than a day or two, but I put the batteries in a bowl on the galley work top, as soon as I return, I refit them.