Discussion on elevated CO2 levels and how to recognise them

[footleg]

I've started this in a new topic because it was an interesting discussion point but hidden in the Shatter Pot thread (sorry for only chopping out the serious bit of your comments Joel! Readers can follow the quote link below for the original post in full):

If you recognise the signs then you should get away with it.  We took an oxygen analyser down a cave in France that we were exploring beyond sumps once and there was only 15% oxygen.  We'd been panting, labouring hard and generally being feeble for days.  Prior to that we couldn't decide if we were just worn out or not...... 

It is worth pointing out that reduced oxygen levels and increased CO2 levels are two different things. While an increase in carbon dioxide (CO2) might be related to a corresponding decrease in oxygen (O2) this is not necessarily always the case. We have evolved to respond to increased CO2 levels, this gas being a by product of our own respiration. It is a sign of impending suffocation so the human sensory system detects it and responds with hyper ventilation and a feeling of being out of breath.

But we are not actually very good at detecting a lack of oxygen when there is not a corresponding increase in CO2 (e.g. If the oxygen was displaced by Nitrogen (N2) which makes up 75% of air normally). In this case we are likely to start acting a bit like we are drunk and light headed, but I've been told you are more likely to spot this in other people than realise it is affecting you.

Note also that the recent case of carbon monoxide (CO) encountered in a cave in Derbyshire (reported in Descent and discussed on this forum) is a different and far more dangerous gas. CO is most commonly formed as a combustion by product where the oxygen supply is limited. With plenty of oxygen it gets converted to CO2 normally. CO is extremely poisonous and we do not generally notice it until it is too late. It binds to the haemoglobin in our blood in place of Oxygen, but does not easily unbind again, so enough exposure takes up most of the oxygen transporting ability of out blood and quickly kills. Symptoms if you get low exposure include a severe headache. Higher levels result in unconsciousness and death. Carbon Monoxide is thankfully extremely rare in caves.

Carbon Dioxide is more common, being a by product of decomposition, and heavier than air. So it can settle in places where there is limited air circulation and build up from sources like rotting vegetation.

Please anyone with medical knowledge feel free to add to or correct anything I might have got wrong in the above!

 

[Brains]

I have also noticed feeling hot, sweaty and irritable, with a longing for the outdoors as symptoms of CO2 elevation, in addition to the symptoms mentioned above.
This was experienced on a Swildons short round during drought when the stream was dry to below the twenty. A hangover is often assumed to be the cause in many instances, but this is not always the case.

 

[cap n chris]

http://cscc.org.uk/Documents/DGC_2003.11.16_CO2_Article.htm

 

[Smithers]

Slightly off topic, but in a small scale dig where capping is involved, I'm guessing that you will decrease the concentration of oxygen, as well as increase CO2, but what impact will the fumes from capping have? 

Its just that I've noticed that after long capping sessions, spending about 6 hours in total capping (alternating between at the head of the dig, seconding with the spoil and emptying the spoil at position 3) that I and my fellow diggers have the most tremendous headaches.  I'm guessing this is due to the noxious fumes from capping rather than the lack of or decrease in oxygen, but then again this site is rather isolated and the rates of energy exchange and air circulation probably aren't that great, although they have improved recently.

 

[Maisie Syntax]

For the vast majority of people, it is carbon dioxide that keeps you breathing. The oxygen you breath in is used in metabolism at a cellular level. Oxygen gets from your lungs to the various cells by being transported in your blood attached to the haemoglobin (iron) inside  your red blood cells. A waste by-product of metabolism is carbon dioxide. The carbon dioxide leaves the cells, but instead of it attaching to your haemoglobin, it (usually) is dissolved into your blood (carbonic acid).

The increase in carbon dioxide/carbonic acid makes the pH of your blood slightly more acidic than it wants to be to keep things running smoothly. The acidty of your blood is constantly & automatically monitored by various parts of your body. The general response of the body to increases in the acidity of blood is to 'blow off' (steady now) the excess carbonic acid which leaves your body in the form of carbon dioxide.
The end result of all this is that if carbon dioxide levels in your body increase, for whatever reason, then the acidity of your blood increases. When the acidity of your blood increases, regardless of the amount of oxygen around or your level of (in)activity, you will start to breath faster and deeper.

General thing to remember when caving (but probably more so mine exploring) is that if you are aware of feeling short of breath / breathing deeper and it isn't because you are an unfit fat b*****d (or thin b*****d - lets not be prejudiced) then the possibility of it being due to raised CO2 levels should be considered.

What to do? Stop and don't go any further is probably a good idea. If reversing your tracks brings a relief to the symptoms, then it could well have been raised CO2. Obviously common sense comes into it. If there is a howling draught like there is on all my digs, then you are unlikely to be troubled by CO2. If you are nearing the end of some long & low collapsed workings in a bone-dry mine, then CO2 is rather more likely to be present.

Incidently, there are some people in which the CO2 respiratory drive no longer functions (long standing chronic lung conditions). For these people, it is the very low levels of oxygen in the blood that triggers respiration. When such people are admitted to hospital, it is often tempting to give them oxygen as they appear short of breath. This can have the peculiar side effect of them stopping breathing, which can be quite alarming for the first few times it happens. If low oxygen levels are the only thing that triggers breathing, then giving oxygen removes the trigger and thus stops you breathing, which is a bit of a design flaw really.

Anyone want to elaborate on carbon monoxide and the oxyhaemoglobin-disassociation curve and hyperbaric treatment?

 

[fuzzy-hair-man]

A good link on CO2 in caves:

http://wasg.iinet.net.au/CO2ASFpaper.html

We have a lot of CO2 in our caves, general procedure is to take a cigarette lighter with you (I've never seen a gas meter/analyser), if the cigarette lighter burns you're OK if not it's getting time to head out. Taking matches also works if the match head burns but not the wood it's getting marginal if the wood burns it's OK, but when someone has been striking matches it makes the cave smell :yucky: so I tend to take a cigarette lighter.

It's often possible to find the CO2 layer using a cigarette lighter if you light the lighter and then lower it down into the CO2 layer the flame will leave the head of the lighter and be sitting in space it's a really cool trick.  8)

Descending into a pit of CO2 is a bad business, the layer is are sometimes more distinct and you are much more quickly and easily able to move down into the layer, and because you aren't exerting yourself you won't pick it up with breathing until you hit really bad CO2. The changeover and prusiking take up lots of effort so you might be lucky to make it back above the CO2 in time  :blink:

and CO2 is not like squeezes or vertical work or whatever it doesn't matter how good, comfortable, experienced you are you can't breath CO2!! it will get you anyway.

Quite often I find I'm lethargic and have a slight headache going into the next day after being in tolerable but high levels of CO2. Of course I get headaches whilst I'm in the CO2 too, I find further to what "in cumbria" was saying that is important to know what your usual breathing rate is for a certain amount of activity so then you don't just put it down to working harder or being unfit but instead check the CO2. 

 

[Duncan Price]

We have a lot of CO2 in our caves, general procedure is to take a cigarette lighter with you (I've never seen a gas meter/analyser), if the cigarette lighter burns you're OK if not it's getting time to head out. Taking matches also works if the match head burns but not the wood it's getting marginal if the wood burns it's OK, but when someone has been striking matches it makes the cave smell :yucky: so I tend to take a cigarette lighter.

The cigarette lighter (piezo is better than flint) detector is pretty good.  As the CO2 level increases the burning flame front moves away from the lighter.

One effect of elevated CO2 that is not to be underestimated is its narcotic effect which can lead to a feeling of doom or lethargy.  I witnessed this first hand when one member of our party in Cuckoo Cleaves couldn't find a climb that he'd come down on the way in.

 

[Prince of Darkness]

You have to look for the obvious signs

 

[fuzzy-hair-man]

The cigarette lighter (piezo is better than flint) detector is pretty good.  As the CO2 level increases the burning flame front moves away from the lighter.

I've never noticed that other than lowering the lighter into the CO2 layer, basically if it burns at all we consider the CO2 levels OK, I believe you can go on a bit further after the lighter doesn't burn but not too far. It's worth remembering that if you are going down into an area that has tolerable but higher CO2 that it will take more effort to get back out so going in and you might feel fine but coming back out will be a different matter.

Do you find the piezo lighter lights more reliably or is there another reason you prefer them?

 

[Duncan Price]

The cigarette lighter (piezo is better than flint) detector is pretty good.  As the CO2 level increases the burning flame front moves away from the lighter.

I've never noticed that other than lowering the lighter into the CO2 layer, basically if it burns at all we consider the CO2 levels OK, I believe you can go on a bit further after the lighter doesn't burn but not too far. It's worth remembering that if you are going down into an area that has tolerable but higher CO2 that it will take more effort to get back out so going in and you might feel fine but coming back out will be a different matter.

Do you find the piezo lighter lights more reliably or is there another reason you prefer them?

Before the lighter won't work at all the flame will move away from the gas jet and "dance" above it with a blue colour.

Piezo is better than flint because if you try to strike a flint lighter with wet hands then the flint gets wet and won't work.

 

[mrodoc]

Footleg's and in Cumbria's? postings are helpful - in Cumbria? might be a doctor. As a diver and caver  I have found CO2 causes different effects depending on circumstances. On rare occasions in diving I have a developed a splitting headache secondary to CO2 retention. It is hard using SCUBA gear to get rid of excess carbon dioxide because of the restrictions imposed by gas viscosity, water pressure and the equipment itself. The acidity of the blood increases and a headache ensues. it also has a contributory effect on narcosis - some have thought most of narcosis is due to CO2 poisoning.

In a cave I tend to hyperventilate and feel panicky with a sensation of not completely filling my lungs. Flushing as mentioned can also occur. Tolerance to CO2 varies widely and there are rare individuals who can tolerate dangerous levels of the gas without being aware of them. Others including me are sensitive to quite small rises in CO2 level.  They are obviously useful members of the party to have on trips!

Hope this helps.

 

[gus horsley]

I had an experience with elevated CO2 levels in Pant y llyn about 25 years ago.  The only supposedly safe entrance is a u-tube which normally has a few inches of water in it.  On this occasion the water had dried out and been replaced by a few inches of leaves which had fallen in.  I entered the descending tube head first as usual and found myself doing fish out of water impressions.  Luckily I managed to back out feet first but I felt so disorientated and confused that it took me a good hour before I could figure out how to drive the car.

 

[Duncan Price]

...As a diver and caver...

...Tolerance to CO2 varies widely and there are rare individuals who can tolerate dangerous levels of the gas without being aware of them...

Pete makes some useful points.  SCUBA divers tend to have an increased tolerance of CO2 through aclimatisation.  Smokers too.  I have a fairly high tolerance of "bad air".

Wikipedia has some useful information on this http://en.wikipedia.org/wiki/Hypercapnia - this has been implicated in causing heart attacks in divers.

 

[Agrophobic]

Having suffered the effects of CO twice i now know how to recognise it, splitting headache and sweating with a strong desire to sleep. feel free to sleep if you are out of the danger area, you feel great afterwards. this was due to exhaust fumes, not in a cave, i'd hope cave levels of CO would be lower.
CO2 and low O2 i havn't experienced and would be keen to know how to tell the difference between just being knackered and suffering air problems.

 

[MatthiasM]

Lack of O2 will kill you painlessly and quickly, no matter how much CO2 is there. You will fall in unconsciousness rather quickly.

 

[solocavediver]

Hi guys, I hate to have to disagree but your lighter is not detecting CO2 it is detecting lack of oxygen. The flame front moves away from the lighter because the gas has to travel further before finding enough O2 to burn. If there's little enough O2 it will of course go out and so should you and I. Detecting CO2 if not accompanied by reduced oxygen requires something more sophisticated. Often the two go together because the CO2 got there when some of the oxygen that ought to be there got burned up. Even if the O2 remains plentiful, excess CO2 will still produce bad symptoms in us though.

              Cheers,

                        Charles.

We have a lot of CO2 in our caves, general procedure is to take a cigarette lighter with you (I've never seen a gas meter/analyser), if the cigarette lighter burns you're OK if not it's getting time to head out. Taking matches also works if the match head burns but not the wood it's getting marginal if the wood burns it's OK, but when someone has been striking matches it makes the cave smell :yucky: so I tend to take a cigarette lighter.

The cigarette lighter (piezo is better than flint) detector is pretty good.  As the CO2 level increases the burning flame front moves away from the lighter.

One effect of elevated CO2 that is not to be underestimated is its narcotic effect which can lead to a feeling of doom or lethargy.  I witnessed this first hand when one member of our party in Cuckoo Cleaves couldn't find a climb that he'd come down on the way in.

 

[Peter Burgess]

Recognizing the symptoms when they affect you is a good start, provided you haven't reached a point of no return!

 

[footleg]

Recognizing the symptoms when they affect you is a good start, provided you haven't reached a point of no return!

Symptoms of Bad Air 101:

 

[Peter Burgess]

Whoops! They've been waiting a tad too long at the Swildons 20 me thinks.

Actually, the thread title is specific to carbon dioxide and not bad air in general. I thought that provided you didn't walk straight into a dangerously high level of carbon dioxide, you would get a warning in the way you felt and performed that might act as an early warning that ought not to be ignored. That's what I was getting at.

 

[fuzzy-hair-man]

Whoops! They've been waiting a tad too long at the Swildons 20 me thinks.

Actually, the thread title is specific to carbon dioxide and not bad air in general. I thought that provided you didn't walk straight into a dangerously high level of carbon dioxide, you would get a warning in the way you felt and performed that might act as an early warning that ought not to be ignored. That's what I was getting at.

Worse than walking into CO2 is abseiling into it! The effort required (and therefore CO2 breathed in) to changeover and get back out is generally more and if you weren't being very careful I reckon it would be very easy to get a long way into CO2 before noticing  as you are abseil you aren't exerting yourself so you aren't doing the exercise etc that would normally help you pickup the presence of CO2 early. This has happened to me and I was doing checks every 2 metres or so on abseil because we knew there was CO2 about and I still got caught, I was really surprised how quickly it changed and how bad the CO2 was.

Hi guys, I hate to have to disagree but your lighter is not detecting CO2 it is detecting lack of oxygen. The flame front moves away from the lighter because the gas has to travel further before finding enough O2 to burn. If there's little enough O2 it will of course go out and so should you and I. Detecting CO2 if not accompanied by reduced oxygen requires something more sophisticated. Often the two go together because the CO2 got there when some of the oxygen that ought to be there got burned up. Even if the O2 remains plentiful, excess CO2 will still produce bad symptoms in us though.

You're not disagreeing, I know it detects a lack of oxygen, just that a lack of oxygen generally accompanies a build up of CO2 (see the link I posted, using a lighter is one of their recommendations), you're right perhaps I should have mentioned that the lighter doesn't detect CO2 but rather lack of oxygen  :-[

Generally I find if I'm in CO2 / low oxygen the lighter won't light at all or that it will light but quickly go out not that the flame front moves away, if it had to move further away from the lighter to find enough oxygen it would also be moving further away from the spark it needs to ignite.  The only time I get the flame moving away is if I light the lighter above the CO2 / lower oxygen and lower the lighter into the CO2 / lower oxygen layer.