Carbon dioxide

[mikem]

The 'open' passage had CO2 levels of about 2.5%, but in the pocket after the collapse, one had 4% CO2, and the was accelerating past 5% so I beat a hasty retreat!

Shafts are also well know to have CO2 collected in the bottom, although maybe this is because it is being generated in the bottom at least as fast as it can diffuse out (so it's not static).

We seem to have two theories about where it comes from - one being a chemical reaction from Iron Carbonate, and the other being oxidation of organic matter.

Chris.

Although, presumably you had a meter that was actually recording the lack of oxygen, rather than the presence of CO2 (there is a big difference in price). CO2 comes from both sources (plus others) & the main supply will vary depending on location.

 

[tomferry]

In, I believe, coal, slate & ironstone mines respectively.

Was this bad air in the slate mine Mike ?

 

[tomferry]

Although, presumably you had a meter that was actually recording the lack of oxygen, rather than the presence of CO2 (there is a big difference in price). CO2 comes from both sources (plus others) & the main supply will vary depending on location.

No it’s a professional 5x meter, used for confined spaces in industry . I have my confined spaces training certification, which they teach you co2 is found at the lowest points.. the o2 missing & the co2 present never add up the same, this is a crucial error why a 5x is a must !

Bob I can accept the co2 is a larger percentage around water, we have seen this on a recent outing. This also shows though that it was the deepest point as water is there ?

In another mine the entrance was 2.2% co2, the end of the mine at the bottom of the dip was 3.6% co2 . Past the collapses at the end to the original working face , is where Chris”s comment is from ,this is the end boarder of the mine “deepest point” This is in a bed of iron ore of a constant thickness and purity, mainly 0 ingress and 0 organic matter ingress .

 

[Fjell]

Purely to add to my fascination, do you always carry an escape set you can get out with when you are doing this?

I have had to put together cascade systems to keep hundreds of people alive, and I do find this using your own body as a canary to be right up there with base jumping to be honest.

 

[royfellows]

The right branch of Taylors Level at Cwmystwyth is notorious. There is a rail across and various warnings. The oxygen is very low but yhe CO2 is not high so the unwitting explorer does not pant or feel any of the familiar signs that an experianced explorer will know. I believe that a lot of the CO2 has dissolved into the water. I am also very familiar with what Chris describes above, mainly in the Nenthead region.

 

[tomferry]

Purely to add to my fascination, do you always carry an escape set you can get out with when you are doing this?

I have had to put together cascade systems to keep hundreds of people alive, and I do find this using your own body as a canary to be right up there with base jumping to be honest.

No 3.5%co2 is turn around point, up to 3% is slow walking then very slow taking footsteps . I believe it’s safe compared to cave diving . After doing it for years and having lots of training, it is normal mine exploring . People pay for similar to train for mountains .

Escape sets are dangerous if your not
Use to fitting them fast , clean shaven etc . You can have a false sense of security .

I am not saying this is safe by any means . It’s mine exploring to start with . Driving to the mine is not safe either , we all calculate are own risks in our hobby .

 

[BikinGlynn]

Browns Folly is limestone. Worsening CO2 in caves seems to have more to do with what's being spread on fields above

This is interesting as yes the mines in question are below flat farmed land, where the majority of others are not, this could be a significant factor.

 

[royfellows]

A tale to shock, yes.

About year 2000 I visited the SS Great Britain at Portsmouth with a lady friend with whom I used to do a lot of exploring. We descended a stairway close to the engine room and at the bottom we both stopped. My lady turned to me and said, "Do you feel what I am feeling", I told her that I did, we had been there before, bad air.
I spoke to one of the personell and explained the situation and afirmed that action was need and this information should go to the highest level. He then admitted that they had a lot of people complaining of headaches after coming out of the hull, and no one had any idea why. He appeared quite disturbed by it. They had volunteers working in there on the closed days with wire brushes applying red oxide, what a healthy job!

 

[BikinGlynn]

Sorry, it is wrong to say there is no air movement. Crudely, whilst the movement of bulk air may cease so it feels as if the air is still, the molecules of various chemicals such as CO2, O2, N2 and others which make up air are still moving. It is this movement of individual molecules which cause diffusion. (You may not realise it but you do feel these individual molecules, not individually but in bulk as pressure on your skin.)

Please think of air as a vast number of molecules which are moving randomly in all directions. Now take a container with an internal dividing wall. On one side we have molecules of O2 & N2 (that is air) and on the other side we have molecules of CO2. If we remove the wall (without disturbing things), those molecules of CO2 which were moving toward the now removed wall will continue onwards into the other half of the container. And like wise, those molecules of N2 & O2 moving towards the wall in the other half will pass into the first half. I hope you can accept that eventually the molecules will mix and the concentrations of CO2, O2 & N2 will be the same across the whole of the container. It is (almost) impossible to reverse this process. So one does not get CO2 concentrating out of air, rather one gets CO2 diluting into air.

If you want to get a visual appreciation of diffusion, then watch

(though convection currents similar to 'wind' are also at work).

Yes some rocks can create CO2 under the right conditions (including limestone). And rocks like coal can have trapped CO2 from when the coal was formed from rotting vegetation (as well as gases like CO - carbon monoxide - white damp). Which is why disused coal mines are very dangerous / suicidal to enter. Also it is possible that rotting wood and other materials taken into a mine can create CO2.

CO2 dissolves in water (just like sugar). The more pressure of CO2 in the air above the water, the more CO2 dissolves into the water. I am going to ignore the complex chemical reactions which can take place. But I will point out that if the water is transported to a different place (i.e. through fissures in limestone rock into a cave passage with ordinary air), then because the pressure of CO2 above the water is lower, the CO2 will come back out. Hence the presence of higher levels of CO2. Normally the CO2 will diffuse into the air (or indeed be blown around such as by a strong stream) and not be noticeable. But some times it takes a while to diffuse and is noticed.

As has been mentioned one can also get oxygen depletion in mines. Usually CO2 levels do not significantly rise so what one suffers is lack of oxygen not elevated CO2. In fact the science of levels of O2, N2, CO2 and other gases such as CO and CH4 in mines is incredibly complex and beyond my level of competence. You also need to understand the instruments which measure gases in air as well. Some misleadingly just measure the oxygen level and for values below 21%, assume the difference is due to CO2 and report it as CO2, ignoring the potential for oxygen depletion.

By the way, so far I only know one person who died in a mine due to bad air (the generic term) so please don't become the second person. I won't say good luck, rather I will say get educated.

Interesting, the highest C02 we have experienced (around 4%) was in a dry area of the mine, however this was prob only 100m from flooded tunnels so I assume the gas has been produced by water ingress.
o2 levels were what everyone said was the dangers in our ironstone mines, but tbh we have rarely experienced a drop below 19.5 & have been in these for years & covered many miles.

 

[BikinGlynn]

So we are saying that natural diffusion of gases ensures that O2, N and CO2 are all well mixed in a given void.

But there are sometimes localised pockets where this doesn't happen. I have seen this a couple of times recently, both times in ironstone after going over a collapse.

View attachment 16669
The 'open' passage had CO2 levels of about 2.5%, but in the pocket after the collapse, one had 4% CO2, and the was accelerating past 5% so I beat a hasty retreat!

Shafts are also well know to have CO2 collected in the bottom, although maybe this is because it is being generated in the bottom at least as fast as it can diffuse out (so it's not static).

We seem to have two theories about where it comes from - one being a chemical reaction from Iron Carbonate, and the other being oxidation of organic matter.

Chris.

I think the second theory sounds correct, water collecting organic matter & potentially pesticides on its journey through to the tunnels.
Nice pic BTW is that @tomferry

 

[ChrisJC]

Purely to add to my fascination, do you always carry an escape set you can get out with when you are doing this?

No, just a 5x measuring O2, CO2, CO, H2S and CH4. It beeps a lot, but it's watched like a hawk!

Chris.

 

[tomferry]

So iron carbonate what exactly is happening to create so much co2 ?? .

If there is no wood , no water . Ventilation is playing a part also little o2 is reaching the end of the mine , this iron carbonate is still creating co2 which eventually becomes a large level say 5% + all of the mine is creating this, but the little ventilation we have is helping so we get lower percentage of co2. over many more years take toll no people go there now it’s 7% .
Unless we have a massive storm and a significant change of atmospheric pressure, I assume this will balance out eventually and end .
Behind the end collapses of a mine like the drawing , am I correct in believing since it’s a pool ,past a collapse it does pond here. it’s a time capsule and the air goes above this there is no ventilation no travel it’s just still and still occurring.

 

[tomferry]

We will call it the Thomas ferry theory 🤯🥸🤠👨‍🚒

 

[shotlighter]

View attachment 16674

So iron carbonate what exactly is happening to create so much co2 ?? .

If there is no wood , no water . Ventilation is playing a part also little o2 is reaching the end of the mine , this iron carbonate is still creating co2 which eventually becomes a large level say 5% + all of the mine is creating this, but the little ventilation we have is helping so we get lower percentage of co2. over many more years take toll no people go there now it’s 7% .
Unless we have a massive storm and a significant change of atmospheric pressure, I assume this will balance out eventually and end .
Behind the end collapses of a mine like the drawing , am I correct in believing since it’s a pool ,past a collapse it does pond here. it’s a time capsule and the air goes above this there is no ventilation no travel it’s just still and still occurring.

Good lord, someone else sad enough to have a copy of Penman's Mine Ventlation!

 

[mikem]

Was this bad air in the slate mine Mike ?

Apparently so, he was a diver.

A tale to shock, yes.

About year 2000 I visited the SS Great Britain at Portsmouth

Great Britain was supposed to go to Portsmouth, but has been in Bristol since 1970, presumably you mean the Warrior...

 

[tomferry]

Good lord, someone else sad enough to have a copy of Penman's Mine Ventlation!

I have a couple ventilation books , also the timbering of mines . Metal mining & other colliery stuff.

 

[Cantclimbtom]

I remember that something acidic mixed with carbonate and water fizzed up a lot.

Presumably if there's some acidic water (perhaps something sulphurous?) that came on contact with Iron Carbonate (FeCO3, siderite) there could be quite a lot of CO2

 

[royfellows]

Apparently so, he was a diver.

Great Britain was supposed to go to Portsmouth, but has been in Bristol since 1970, presumably you mean the Warrior...

We visited both ships, but feel certain it was the Great Britain in which case I have confused the location with the other. The SS Great Britain was lying abandoned and beached in the Falklands which sits with the amount of rust I remember in the hold. It was lit up well although visitors were prevented entry to that section still under renovation. It must have been Bristol, we were visiting Box and saw it signposted from the MWay, posting this from memory, and this was gave us the idea for the visit. This then lead to the Victory and the Warrior.

 

[ChrisJC]

I remember that something acidic mixed with carbonate and water fizzed up a lot.

Presumably if there's some acidic water (perhaps something sulphurous?) that came on contact with Iron Carbonate (FeCO3, siderite) there could be quite a lot of CO2

This agrees with my thinking.

We have two independent effects:
Iron oxidising reduces the amount of O2.
Iron Carbonate (siderite) reacting with sulphuric acid generates CO2.

Chris.

 

[tomferry]

Yes I agree I think we have a good understanding.