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Mine Exploration Forum

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Author Ventilation in mines and caves
Lindybeige

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Ventilation in mines and caves
Posted: 10/11/2020 02:13:00
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Hello. I am researching ancient and medieval mines. Mines go back to the stone age (e.g. Grimes Graves) and there are some spectacular bronze-age mines in Cornwall. I posted this on a caving group, and one reply was the suggestion that I post it again here.

Where I am interested in what the people here might know about is underground ventilation. Modern mines are comparatively easy to ventilate, thanks to electric motors and air propellers.

I am trying to work out what in an ancient mine excavated by archaeologists might have been dug out not for ore, but for ventilation. One way to look at this problem is to have a look at underground spaces that were not created by Man, and where ventilation for mine workers was a not a design consideration - natural caves, and to see how they vary.
Here are some questions, and if anyone here can tackle them, then please do.

In cave systems with more than one entrance, how common is natural air movement from one entrance to another? How strong does it get? How well-ventilated are cul-de-sac offshoots from the path of the air movement?

Do you have a rule of thumb for how many people can breathe safely in a volume of cave? How much difference would it make if you were hard at work mining, with hammers and chisels, rather than just sitting there admiring the stalactites?

If there is a fresh supply of air in one section of a cave, how far sideways into an unventilated section could you venture without needing modern breathing equipment? What about vertically?

When there is not enough good air, what happens? Do people start getting sleepy? What is the biggest problem? Is it carbon dioxide build-up? Can you escape that just by climbing ? Is it lack of oxygen? Is it quickly obvious to a caver when there isn't enough air, or can the danger creep up on you? If the problem is CO2, then as I understand it, this makes people sleepy and contented, which makes it extra-deadly. On the other hand, I would have thought that a lack of oxygen would be quite different - more likely to cause panic.

If you had a burning candle and were exploring a badly-ventilated cave, what would happen first - the candle goes out or you are incapacitated?

Are there caves where artificial ventilation shafts have been added, and did these work?

Are there big seasonal variations with ventilation?

I am aware that some natural caves have other unusual and dangerous gasses in them, but let us assume that the problem is just an absence of ventilation from the surface.

In caves with just one entrance, is a lack of air a massive problem, hugely limiting human exploration down there? Do some caves with only one entrance seem like gas-tight pockets, while others seem to get air somehow through unseen fissures in the rock?

Have people solved cave ventilation problems with any low-tech methods? Lighting a fire to create an up-draught near a shaft? Wafting air into the entrance with a big cloth sheet on a stick? Building a chimney over an entrance?

That's rather a lot of questions - sorry about that. Anything that will help me understand what early miners would have had to contend with regarding ventilation is appreciated. I've been talking to modern mining engineers, but I thought that cavers might have a better idea of bad ventilation underground than engineers who work all the time with massive electric ventilation equipment and modern ducting.
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Down and beyond

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Ventilation in mines and caves
Posted: 10/11/2020 06:56:10
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Quote : When there is not enough good air, what happens? Do people start getting sleepy? What is the biggest problem? Is it carbon dioxide build-up? Can you escape that just by climbing ? Is it lack of oxygen? Is it quickly obvious to a caver when there isn't enough air, or can the danger creep up on you? If the problem is CO2, then as I understand it, this makes people sleepy and contented, which makes it extra-deadly. On the other hand, I would have thought that a lack of oxygen would be quite different - more likely to cause panic.

If you had a burning candle and were exploring a badly-ventilated cave, what would happen first - the candle goes out or you are incapacitated?


Hello and welcome to addit now that was quite a introduction.
I have copied a section of your post I will focus on this. Section in my reply .I would just like to also say I think focusing on the ventilation in mines in one post would be best as caves are a completely different system and work differently .

First thing I am sure your conversation with a modern mining engineer would have made clear , why is there low o2 this can be caused by so many different reasons .

This is one example of walking into a mine and hitting a co2 pocket .

Within as little as 3 steps you will have multiple things happening to your body head ace normaly gets me first following by gasping for breath heart rate is increasing also at this point muscles starting to ace also . The best thing you can try to do is to stay calm and slowly start figuring your way back out which is a lot easier said than done . At this point you are trying to also figure out what you have encountered what gas is it ? Is it going to follow me back out ? This is when knowledge and experience is important also having the the correct equipment. Your candle will have gone out but if your above 14% o2 you will definitely still be awake unless co2 is extremely high .

You can not really escape this once underground if you find it , in pillar and stall iron mines some times you can go around it but to be honest it’s extremely dangerous and not wise at all .

After re reading your very good large post I am going to try find you some links from previous questions some by me as there is so much information. Would recommend a good search on the site .


https://www.aditnow.co.uk/community/viewtopic.aspx?t=15108

https://www.aditnow.co.uk/Community/viewtopic.aspx?p=205552#msg205552

D&b


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IP: 82.132.212.197 Edited: 10/11/2020 07:34:15 by Down and beyond
ttxela

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Ventilation in mines and caves
Posted: 10/11/2020 08:57:58
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Other folk will have better knowledge of these issues in mines. I deal with LN2 and CO2 in labs a fair bit.

Whilst anxiety and condfusion are often quoted as symptoms of oxygen depletion I'm not sure panic often occurs, this may be more likely when oxygen is reducing gradually perhaps? Where we see accident reports in labs it is usually someone moving very quickly into that environment and unconciousness/death occurs often within a couple of steps of safety Crying

Pure oxygen depletion only occurs with nitrogen being released really, nitrogen being non toxic and making up much of the air already, if extra nitrogen is added, for instance by an LN2 spill it has little option but to displace the oxygen in the air. There is a bit of CO2 in air but the proportion is pretty small.

CO2 however displaces both the nitrogen and oxygen elements of the air and since nitrogen is in the greater proportion it displaces that to a greater extent - thus it is possible to get to problematic levels of CO2 without depleting oxygen to a concerning level - this is admittedly more of a problem when using dry ice or CO2 in cylinders where there is a probability of sudden release. I guess in mines the issue is more of longer term build up (mostly)?

Fortunately I don't have to deal with oxygen enrichment any more - at one point I was running out of wall space for monitors Laugh
IP: 195.171.131.2 Edited: 10/11/2020 08:59:10 by ttxela
Down and beyond

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Ventilation in mines and caves
Posted: 10/11/2020 09:05:36
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The panic sets in because your a long way underground and you normally realise you cannot breath very well your heart rate is on the up all of a sudden and because of the low o2 and co2 build up you cannot do stuff you normally could without thinking as you can’t concentrate properly even remembering your way you came in becomes hard .

Apologies I should have stated that this example happened in a large pillar and stall iron mine where navigating is a critical element every inch looks the same and a slight mess up navigating can be a huge issue .

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royfellows

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Ventilation in mines and caves
Posted: 10/11/2020 09:37:27
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Caves, mines and mines, this shows differences in what can be expected. Caves are natural cavities that usually occur in limestone regions. You wont get gas unless industrial waste has somehow been dumped in.

Mine is a very far reaching term covering everything from coal mines to slate mines, the latter actually being underground quarries. Gasses uncounted underground will be worst in coal mines, and non existent in slate workings.

Your questions really would form the basis of quite a heavy volume and to really expect them be answered on a website, is in fairness a little much.

Re the candle. In the accounts of some of the old miners, a rough quote, "The air was so bad in the ends that a candle would not burn". The candle will go out before you do.

A good start to your research would be the 19th Cent Royal Commission reports into working conditions in mines in Great Britain. Internet searches will turn up quite a lot.

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royfellows

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Ventilation in mines and caves
Posted: 10/11/2020 09:40:31
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Also, Reports of the Inspectors of Mines, 1873, 1874, and 1896.

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staffordshirechina

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Ventilation in mines and caves
Posted: 10/11/2020 09:49:37
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What you are researching is a huge subject and will take you a long time to get your head around.
There are so many factors at play that each mine is an individual ventilation problem. Then there are other considerations like the methods of working, pick, hammer/chisel, fire setting, explosives, etc. They all require different ventilation schemes.

There are examples of ventilation methods still accessible to visit in different parts of the country. Some of us can offer more help if you tell us more about your research and general location.

Les
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Tamarmole

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Ventilation in mines and caves
Posted: 10/11/2020 10:19:44
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As others have said it is a complex subject that cannot be answered in a couple of sentences. However....... As a rule of thumb a candle will not burn in an environment of less than around 16% oxygen whilst a person can function reasonably well down to about 13%. Thus is a candle won't burn it is time to bail. IP: 86.187.165.242
Down and beyond

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Ventilation in mines and caves
Posted: 10/11/2020 10:24:31
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staffordshirechina wrote:

What you are researching is a huge subject and will take you a long time to get your head around.
There are so many factors at play that each mine is an individual ventilation problem. Then there are other considerations like the methods of working, pick, hammer/chisel, fire setting, explosives, etc. They all require different ventilation schemes.

There are examples of ventilation methods still accessible to visit in different parts of the country. Some of us can offer more help if you tell us more about your research and general location.

Les


Lots of are iron mines here had 1 working face with around 15 addits of various sizes some large tramway ones 2 track wide and people addits the mine stretched about 3 miles backwards then around 2 miles wide with no air shafts at all have tried to work the total distance of passage it’s around 100 miles . There are very little photos left of the workings sadly and I have explored large amounts of various mines here have never found any signs of fans or pads where they could have sat on . If we said the age range was 1905-1950 roughly apart from open addits and lighting fires inside would fans be the only other option for ventilation there was never compressed air added so it was all hand drilling and blasting the old fashioned way . Once a section was worked it was bricked up or curtains was added to direct the air flow .

Just wondering about if you no of other ventilation methods that could of been used

Tom

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Coggy

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Ventilation in mines and caves
Posted: 10/11/2020 10:38:05
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Lindebeige, get a copy of Agricolas 'De Re Metallica' it has lots of examples of Medieval mine ventilation.




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pwhole

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Ventilation in mines and caves
Posted: 10/11/2020 11:41:26
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Where workings were in closely-spaced parallel or sub-parallel veins or pipes, ventilation could be drastically improved by the simple expedient of opening 'thurls', or small windows between the workings - this would create a draught due to the differences in air temperature and pressure. Obviously the further away from an entrance the less beneficial this technique would be, but it's quite common to see them in Derbyshire lead mines - there's good examples in Odin and Devonshire mines. I think Cromford Sough was also part-driven as a parallel driveage with connecting thurls due to bad air problems.



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In Moorfurlong Mine in Bradwell there's an air-duct made as a drystone wall sealed with clay, and festooned with miners' fingerprints - this clearly has a void at the back, and was built to convey fresh air into the further reaches of the small-scale pipe-workings, no doubt sourced from a now-blocked climbing shaft up to higher levels close by. A title dispute between 1692 and 1696 included a deposition by a miner, Robert Jowle, who had been employed by the mine owners to "set them a ffan to gain winde". It's entirely possible that this draught duct was part of that system.



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Ventilation in mines and caves
Posted: 10/11/2020 12:10:39
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Another interesting feature was found in Longcliffe Mine, which were the clay remains of a draught door, comprising two uprights stuck to the wall with clay and a lintel sat in two sockets. This was in a tight natural passage used for access between two sections of the mine, and was clearly use to manage ventilation - possibly to reduce the cold for the working miners, as there's certainly no shortage of fresh air, it being so close to Speedwell. There was no trace of any timber lying around, so the door was clearly removed again at a later date by the miners - as we dug our way into the extensions we know no previous explorers have been there. The only remains are the clay impressions of the uprights and a longer patch of clay on one wall where the natural undulations have created a leak behind the upright and the miners have plastered more on to seal it - their fingerprints were instantly visible.

Whether this feature will survive is in doubt, as most people don't notice it until the return journey, and the passage narrows right there - though it does show exactly why they placed it there, and why the open but low bedding beneath has been filled with small-scale spoil.



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IP: 81.174.241.13 Edited: 10/11/2020 12:12:25 by pwhole
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Ventilation in mines and caves
Posted: 10/11/2020 13:17:23
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I have found this in one of are mines before could this be a aid to ventilation ?

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Ventilation in mines and caves
Posted: 10/11/2020 14:56:15
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I would highly recommend talking to PDMHS (Peak District Mines Historical Society), particularly John Barnatt who has published many articles and books on all aspects of ancient mines. A list of articles from PDMHS is available here [web link] IP: 51.9.11.79
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Ventilation in mines and caves
Posted: 10/11/2020 15:31:36
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We recently dug through a collapse in a local Lead Mine. One of the trial drifts into the Great Limestone had the remains of an extensive vent duct made from small sticks and the abundant phreatic clay, rather like wattle & daub. Sadly the whole lot was now on the floor, the wood having long rotted away, but the clay pack still bore the impressions of the wattle core.

I'll ask He-who-has-a-finger-in-every-pie if he's any photos of same.

MARK

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ChrisJC

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Ventilation in mines and caves
Posted: 10/11/2020 15:39:07
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I've not seen this mentioned yet, the word brattice:

https://en.wikipedia.org/wiki/Brattice

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Ventilation in mines and caves
Posted: 10/11/2020 16:15:51
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legendrider wrote:

We recently dug through a collapse in a local Lead Mine. One of the trial drifts into the Great Limestone had the remains of an extensive vent duct made from small sticks and the abundant phreatic clay, rather like wattle & daub. Sadly the whole lot was now on the floor, the wood having long rotted away, but the clay pack still bore the impressions of the wattle core.

MARK


Last intact piece


(click image to open full size image in new window)

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Down and beyond

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Ventilation in mines and caves
Posted: 10/11/2020 16:20:11
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royfellows wrote:

legendrider wrote:

We recently dug through a collapse in a local Lead Mine. One of the trial drifts into the Great Limestone had the remains of an extensive vent duct made from small sticks and the abundant phreatic clay, rather like wattle & daub. Sadly the whole lot was now on the floor, the wood having long rotted away, but the clay pack still bore the impressions of the wattle core.

MARK


Last intact piece


(click image to open full size image in new window)


How wide would this have originally been ? Was this a direct duct to the surface for air flow ? Am a bit lost in exactly what this is thanks .

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Lindybeige

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Ventilation in mines and caves
Posted: 10/11/2020 16:23:50
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Coggy wrote:

Lindebeige, get a copy of Agricolas 'De Re Metallica' it has lots of examples of Medieval mine ventilation.


Good answer! I know, because his work was one of my main starting points for this whole rabbit-hole of research.
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Lindybeige

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Ventilation in mines and caves
Posted: 10/11/2020 16:26:31
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legendrider wrote:

One of the trial drifts into the Great Limestone had the remains of an extensive vent duct made from small sticks and the abundant phreatic clay, rather like wattle & daub.
MARK


Crikey! Any idea what period that was? Was this a horizontal duct within a horizontal passage?
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