Lack of oxygen?

[Sailsalot]

Is it possible to suffer from lack of oxygen/ carbon dioxide build up sleeping in a small cabin on a boat?
We slept on board and are now wondering if that happened to us. We slept in our small fore cabin with the door shut, the fore hatch had a waterproof cover we use to cut out the light, which probably cut out all ventilation and as it was chilly the hatch was closed. We both woke up very short of breath, worryingly so, we noticed our dog sleeping with us was struggling and panting too. After opening the hatch slightly and also the door to the main cabin, all symptoms gradually disappeared.
We’ve only had the boat for 2 seasons and this is probably the first time we’ve slept on board when it has been cold, which might explain why this has not happened before, in warmer weather we’ve had the hatch open slightly.
Has anyone heard of this happening or experienced it themselves?

 

[pvb]

I'd never sleep onboard without some slight ventilation, even in deepest winter.

 

[guernseyman]

At least two vents are needed to allow a flow of air.
At the moment I can count six here.

 

[pcatterall]

'Is it possible to suffer from lack of oxygen/ carbon dioxide build up sleeping in a small cabin on a boat?
Read more at http://www.ybw.com/forums/showthread.php?439862-Lack-of-oxygen#eyt9KXIPZQdetT1w.99'

Yes, of course you may suffer but, I believe, only so much! I think the discomfort in that situation will wake you up rather than put you to (permanent!) sleep.

 

[peteK]

Yes it has happened to me whilst sleeping in the forecabin with the door closed, had to open forehatch before I could breath properly.

 

[andygc]

You are describing hypercapnia, the result of an increase in the carbon dioxide concentration in your local atmosphere. In simple terms, the accumulation of exhaled CO2 in the air you breathe results in your blood becoming more acidic. This has a direct effect on the respiratory centre in the brain, causing an increase in the rate and depth of breathing. You would perceive this as being short of breath. The effect is rapidly reversible on breathing normal air, as you discovered. pcatterall is correct; the discomfort can be expected to wake you up well before your blood concentration of CO2 becomes potentially dangerous. In the situation you describe you will not be particularly short of oxygen. The symptoms are the result of excessive CO2 concentration in inspired air. Even with 5% CO2 you still have about 16% oxygen in the air you are breathing, which is very roughly the equivalent of normal air 7,000 feet up a mountain. You would feel extremely breathless, hot, bothered and unhappy at 5% CO2 in the inspired air.

The situation is nowhere near as rosy if you have heart or lung disease, when tolerance of hypocapnia could be much lower.

 

[runningman]

If an average resting adult needs about 7 litres of air per minute (quick google) for 8 hours, that's 7 x 60 x 8 = 3360 litres x 2 people = 6720 + say 1000 for an average dog = 7720 litres of fresh air in total. Or 965 litres per hour.

If I guess an *average* forecabin *open space* of say 1.4m width, 2.6m length and an average height of 1.5m that's 5.46 cubic metres or 5460 litres.

5460 / 965 = just over 5 and a half hours of fresh air. I would guess it would start to feel stuffy before the fresh air ran out.

Very crude calculations but you get the picture. Best to always ventilate the cabin.

 

[Daydream believer]

If an average resting adult needs about 7 litres of air per minute (quick google) for 8 hours, that's 7 x 60 x 8 = 3360 litres x 2 people = 6720 + say 1000 for an average dog = 7720 litres of fresh air in total. Or 965 litres per hour.

If I guess an *average* forecabin *open space* of say 1.4m width, 2.6m length and an average height of 1.5m that's 5.46 cubic metres or 5460 litres.

5460 / 965 = just over 5 and a half hours of fresh air. I would guess it would start to feel stuffy before the fresh air ran out.

Very crude calculations but you get the picture. Best to always ventilate the cabin.

I would not doubt that for a minute but one needs to take into account that one still breaths out a lot of unused oxygen so the same volume of air can be used a couple of times before becoming uncomfortable
But throw in a curry & few f.rts & the air can give one a severe headache in the morning
Ventilation is the answer ( coupled with a cork of course)

 

[mawm]

If an average resting adult needs about 7 litres of air per minute (quick google) for 8 hours, that's 7 x 60 x 8 = 3360 litres x 2 people = 6720 + say 1000 for an average dog = 7720 litres of fresh air in total. Or 965 litres per hour.

If I guess an *average* forecabin *open space* of say 1.4m width, 2.6m length and an average height of 1.5m that's 5.46 cubic metres or 5460 litres.

5460 / 965 = just over 5 and a half hours of fresh air. I would guess it would start to feel stuffy before the fresh air ran out.

Very crude calculations but you get the picture. Best to always ventilate the cabin.

But you only need about 250ml of O2 per min and produce 200 ml of CO2/min. In your example, and taking the dogs requirements as equal to a humans, that is 400 l available per person/dog (O2 in air is about 21%). It would take quite a bit of rebreathing of the air in the cabin to lower the partial pressure of O2 to dangerous levels.

Five percent CO2 will certainly make you breathe a bit faster, it is not life threatening but might get a bit hot, have a racing heart and headache. You'd need a fairly airtight cabin for this to happen.

 

[Mariner69]

Have you had any flames burning; cooking, lighting, warming?

There is always a risk of carbon monoxide build up so you might sleep happier if you have a twenty quid carbon monoxide detector in the space just in case it is that rather than just the lack of ventilation. A small amount of that gives a cracking headache after exposure.

Ventilation will also carry away the water vapour you breath out so it doesn't drip on your forehead in the morning.

 

[Sailsalot]

Thank you for your replies they are quite re -assuring, hopefully no lasting damage to ourselves or our dog! We were actually quite worried at the time as it didn’t immediately occur to us that it was the carbon dioxide build up causing our breathing difficulties. With hindsight it is obvious that the mistake we made was putting an outside cover on the hatch, stopping the air flow working in the vent. We foolishly hadn’t fully thought out the consequences of sleeping in what in effect was a fairly well sealed container. I think most small cruising boats have the same single vent in the fore cabin, our boat is 20 years old, perhaps newer ones have more vents.
On a cold night it is tempting to shut everything to keep warm, but not a mistake we will be making again.

 

[guernseyman]

It should be pointed out that you have a large and adjustable ventilator in your companionway, and weather boards.
Years ago my wife made a cloth fill-in for the companionway, hanging from a replica of the top weatherboard. It's not air-tight so it allows plenty of air past. But it's still adjustable, by inserting one or more weatherboards.

 

[Tam Lin]

+1 on the carbon monoxide warning. People have died on their boats with heaters on and not enough ventilation.

 

[Sailsalot]

Thanks for mentioning carbon monoxide as a warning, we do actually have an alarm for that on the boat and it didn't go off, that would have been much more serious.

I think we should fit a vent in the cabin door as well, have looked at photos of other newer boats the same model and they have a large vent there, other precautions would be to leave the cabin door open as the main cabin has other vents -and of course not block the only vent on the roof of the cabin.

Sunday was the coldest night we’ve spent on board so far and a lesson learnt about the need for adequate ventilation.

 

[bedouin]

I always have to have ventilation when sleeping - even in a normal house I will have a window open. Without that I can wake up with a mild headache and feeling generally unwell. Also I would think if you slept in an ventilated fore peak you would wake up with condensation raining from the deckhead.

 

[Fantasie 19]

Have you had any flames burning; cooking, lighting, warming? There is always a risk of carbon monoxide build up so you might sleep happier if you have a twenty quid carbon monoxide detector in the space just in case it is that rather than just the lack of ventilation.

+1.. I was thinking that

 

[skyflyer]

Also bear in mind that CO2 is denser than air and oxygen so - once the temperatures have equalised - in a calm unventilated space it will tend to settle towards the bottom of the cabin. Not completely because there will be some mixing by diffusion and motion of the air but it might mean that the distribution of Oxygen will not be equal.

 

[gasdave]

Using Runningman's average completely sealed forecabin of 5460 litres:

At 21% oxygen this would provide sufficient oxygen for 3 resting/sleeping adults (@ 250ml/min each) for approximately 25 hours.
Those 3 adults would produce, @ 200ml/min each, sufficient carbon dioxide to create a 5% atmospheric concentration in the cabin after approximately 7.5 hours.

At about 3% they would experience an increasing heart rate and breathing rate would already be up. By 5% there would be headaches and impaired cognition and rapidly increasing danger of death by 10%, or at 15 hours in this cabin (in fact in less time than that as the production of carbon dioxide would increase exponentially with increasing metabolic rate driving the faster heart rate, panic, etc.).

Carbon monoxide toxicity on the other hand would induce sleepiness and unconsciousness without necessarily other warning signs - hence the importance of a reliable alarm. The danger of odourless invisible CO is that it would ensure you would sleep happily even in the absence of an alarm.

We always sleep in an open forecabin, preferably with an open vent/hatch (if Mrs Gasdave allows it). Apart from anything else it reduces the amount of condensation produced in a confined space. Those same 3 sleeping adults might produce as much as 500ml water in expired breath (@ 100% relative humidity) over 8 hours.

 

[Halo]

Excess CO2 is what triggers the urge to beathe when you are swimming under water. In the old days people used to hyperventilate to purge CO2 from the body and delay the breathing "burn" when snorkelling. Unfortunately this can result in you going unconcious so it no longer the done thing.
You will only be comfortable overnight in a small cabin if you have ventilation. Ways to avoid the ventilation itself being an issue are
1. Get a really warm sleeping bag or put on sleeping bag inside another
2. Wear a tee shirt in bed (plus thermals if necessary
3. Work out how not to get draughts on you
4. If you have shore power leave a silent convector heater on all night
5. get SWMBO a lot water bottle
6. Get yourself a nice bottle of whisky and have a few before retiring
7. Sail to carribean

 

[ShinyShoe]

People do die from CO2 in confined spaces. There are numbers above that I have no reason to dispute that suggest the conc would be between 5-10% overnight.

As someone said CO2 sinks the conc will be higher low down (where your head is).

If you feel like sh1te and don't realise why you wont necessarily realise that the right thing to do is get out the space instead you may lie down coz you feel like sh1te and hope your stonking headache and racing heart passes...

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Double check CO though as well. Its same denisty as air so doesn't sink. Any possibility CO production could be leaking into the forepeak?

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Worried about venting to the cold then provided its not breaching a watertight bulkhead I'd vent to the cabin and vent the cabin. But beware if the cabin has CO in it so will the forepeak...