POOR AIR, 2007

[cap n chris]

Had first report of poor air on Mendip in 2007; given that this winter is so exceptionally mild, unless we have a cold snap there is a strong likelihood that 2007 will see a return of the build up of poor air in some of the "usual suspect" locations. However, for starters here's what we know so far:

Little Crapnell Swallet - poor air experienced January 3rd at Uriah Creep. It is expected that Honeymead Hole will be similarly affected.

 

[Hammy]

While on the subject of poor air I had an 'interesting' experience a couple of days ago in a very innocuous little cave near Silverdale in Lancashire - Hale Moss Cave.

I was about 40m in at a guess in a small phreatic tube past a squeeze, round several right angle bends and on my own when I suddenly realised my breathing rate had increased rapidly and I had a very strong urge to get out fast! Had to backwards crawl for a way until I could turn round and shot out like a rat out of a drainpipe feeling pretty scared!

There was no draught in the cave at all. It's my first experience of low oxygen/high CO2 and one I won't forget in a hurry!!

Anybody else been in Hale Moss Cave?

 

[graham]

I think Chris is spot on with this. I, sadly, predict closed caves on Mendip this summer.

 

[Dep]

Had first report of poor air on Mendip in 2007; given that this winter is so exceptionally mild, unless we have a cold snap there is a strong likelihood that 2007 will see a return of the build up of poor air in some of the "usual suspect" locations. However, for starters here's what we know so far:

Little Crapnell Swallet - poor air experienced January 3rd at Uriah Creep. It is expected that Honeymead Hole will be similarly affected.

Your comment suggests a correlation between weather conditions and cave air quality. I was not aware of this, what are the effects and causes etc etc.

 

[graham]

Had first report of poor air on Mendip in 2007; given that this winter is so exceptionally mild, unless we have a cold snap there is a strong likelihood that 2007 will see a return of the build up of poor air in some of the "usual suspect" locations. However, for starters here's what we know so far:

Little Crapnell Swallet - poor air experienced January 3rd at Uriah Creep. It is expected that Honeymead Hole will be similarly affected.

Your comment suggests a correlation between weather conditions and cave air quality. I was not aware of this, what are the effects and causes etc etc.

We don't know for certain, but one of the favoured theories at the moment is that in warmish wet winters (like this one) the breakdown of vegetable matter never ceases & greater quantities of CO2 are available. There's more to it than that, but that's the main point.

 

[whitelackington]

Why would you get bad air in the connecting Ladder Dig extention in G.B.
could not be rotting material in there as seven metres above streamway, carbon dioxide is heavier than air.

 

[graham]

Why would you get bad air in the connecting Ladder Dig extention in G.B.
could not be rotting material in there as seven metres above streamway, carbon dioxide is heavier than air.

I would have to look up the data that we collected last time, but the short reply is that when the cave was closed there were high levels of CO2 in the Gorge & the Main Chamber & you could not safely get near the Ladder Dig, anyway.

 

[whitelackington]

About two or three years ago, we B.D.C.C. got as far as the duck in Ladder dig extention with no problem, then as the first person went through the duck,
the rest of us, resting, suddenly realised we were short of breath, it very quickly got bad, so reluctantly we left the cave, it was tiring climbing back up, not sure if that was poor air, we had not noticed it untill waiting to go through the duck, in L.D.E.
Being tired climbing up could have been partially caused by wanting to get out fairly quickly.  Probably, was also bad air that we did not notice on the easy trip down.

Latter that evening, probably the least fit person, not me,
honked their guts up. :yucky:

 

[graham]

About two or three years ago, we B.D.C.C. got as far as the duck in Ladder dig extention with no problem, then as the first person wet through the duck, the rest of us, resting suddenly realised we were short of breath, it very quickly go bad, so reluctantly we left the cave, it was tiring climbing back up, not sure if that was poor air, we had not noticed it untill waiting to go through the duck, in L.D.E.
being tired climbing up could have been partially caused by wanting to get out fairly quickly.
Latter that evening, probably the least fir person, not me,
honked their guts up. :yucky:

Ok, you are describing the effects of bad air, certainly. I suspect that the levels were raised throughout the cave and you only really noticed it when three of you were waiting in a fairly confined space and your own output pushed the CO2 level just that bit higher.

 

[whitelackington]

One other thing to bare in mind with bad air, the more people on a trip, if their is a problem, the quicker it goes from poor to serious

 

[Peter Burgess]

Why would you get bad air in the connecting Ladder Dig extention in G.B.
could not be rotting material in there as seven metres above streamway, carbon dioxide is heavier than air.

I would have to look up the data that we collected last time, but the short reply is that when the cave was closed there were high levels of CO2 in the Gorge & the Main Chamber & you could not safely get near the Ladder Dig, anyway.

Are you implying a connection between the cave closure and bad air? Surely not - I can't believe that because the gate wasn't opened a few times each weekend, and no cavers explored the system for a while that the carbon dioxide levels suddenly shot up. There was surely some other factor at work, and the cave closure was coincidental.

 

[cap n chris]

Your comment suggests a correlation between weather conditions and cave air quality. I was not aware of this, what are the effects and causes etc etc.

I rather favour John Gunn's Cold Trap Theory:

IIRC, to summarise: cold air is heavier than warm; therefore at a cave entrance in winter cold air trickles into the depths of the cave, displacing the warmer air within it (i.e. cold air "falls" into the cave and "pushes" out the air back up, thereby purging the cave of the air which is within) - the net result is that the contents of the cave are refreshed.



Also, be aware that there are LOTS** of other factors which can affect CO2 levels in caves and there may well be an interplay of the various (complex) dynamics which cumulatively result in the problem. Everyone will probably have their own 2p on what causes the problem and everyone may be partially correct. I've tried to enthuse students to do a Ph.D on this but the mathematics of cumulative CO2/breathing scares them off - even failed to get a response from a geeks' maths forum when I posed them the breathing model for them to have a go at. Put simply:

* People breathe at a particular rate, dependent on the CO2
* As CO2 increases, they breath quicker, exhaling more of their own CO2 which makes them breathe quicker still
* In a given volume space with air of a particular CO2 percentage, what is the breathing rate/CO2 curve as things go from bad to worse?
* How long before the person(s) are breathing CO2 of 10+%?

_________________________

** Some factors affecting CO2 levels in caves may include:

1) Rotting vegetation
2) Farming - nitrates, manure etc.
3) Number of people visiting/breathing
4) Surface vegatation, humic acid/acid aggressivity - water entering the cave dissolving the limestone resulting in release of CO2
4) Global warming has been posited as a potential element affecting CO2 underground - certainly, if CTT is correct (above) then this would mean that following a warm(er) winter there is poor air in the summer - pretty much what we've been observing, BTW); added to this would be the lower level of vegetation dying back which would mean less humic acid aggressivity but offset with an increase in vegetative growth which would ultimately result in a great die back at some later stage.
5) It is worth noting that poor air was recorded in Mendip caves in the 50s so it's not a recent phenomena - I don't have a record of which year(s) were reported as poor air ones but it should be possible to check Met Office archives to see if there was a warm(er) winter in the run-up to the poor air reports.
6) Surface run-off - significant streams/water entering the cave brings fresher air with it.
7) Cave pixies
8) Etc. - your theory goes here

 

[graham]

Why would you get bad air in the connecting Ladder Dig extention in G.B.
could not be rotting material in there as seven metres above streamway, carbon dioxide is heavier than air.

I would have to look up the data that we collected last time, but the short reply is that when the cave was closed there were high levels of CO2 in the Gorge & the Main Chamber & you could not safely get near the Ladder Dig, anyway.

Are you implying a connection between the cave closure and bad air? Surely not - I can't believe that because the gate wasn't opened a few times each weekend, and no cavers explored the system for a while that the carbon dioxide levels suddenly shot up. There was surely some other factor at work, and the cave closure was coincidental.

Errm, I'm talking about when we closed it because of the bad air.

 

[graham]

5) It is worth noting that poor air was recorded in Mendip caves in the 50s so it's not a recent phenomena - I don't have a record of which year(s) were reported as poor air ones but it should be possible to check Met Office archives to see if there was a warm(er) winter in the run-up to the poor air reports.

Only partially true. Whilst it is the case that some caves have been known for bad air for a very long time, we have NO reports of bad air in G.B. from when it was discovered in the 1930s up until the year it had to be closed for this reason a couple of summers ago.

Whatever the cause is, something - changes in land use, changes in use of fertilizers, global warming, rise of fundamentalist religions, whatever - has changed on Mendip (I have not heard similar reports from other regions) in recent years.

 

[cap n chris]

5) It is worth noting that poor air was recorded in Mendip caves in the 50s so it's not a recent phenomena - I don't have a record of which year(s) were reported as poor air ones but it should be possible to check Met Office archives to see if there was a warm(er) winter in the run-up to the poor air reports.

Only partially true. Whilst it is the case that some caves have been known for bad air for a very long time, we have NO reports of bad air in G.B. from when it was discovered in the 1930s up until the year it had to be closed for this reason a couple of summers ago.

Whatever the cause is, something - changes in land use, changes in use of fertilizers, global warming, rise of fundamentalist religions, whatever - has changed on Mendip (I have not heard similar reports from other regions) in recent years.

Yes, sorry; forgot about that! In which case, at GB Cavern, it could be CTT in conjunction with changes in farming practices since the catchment doesn't have much else happening to it before it goes straight underground - I doubt if prevailing weather/air pollution would be relevant either, since most of the rain comes straight in off the Atlantic! I suppose it could be something to do with religion, or perhaps even obesity.

 

[whitelackington]

I would imagine that it is at least partly to do with bacteria, isn't everything.
Have any scientific test been done in Mendip caves to see if we have any unusual bacteria eating our walls.

 

[Peter Burgess]

Carbon dioxide can be the product of both biological processes (e.g. brewing) or chemical processes (acidic water attacking limestone). Either or both could be occurring.

 

[paul]

5) It is worth noting that poor air was recorded in Mendip caves in the 50s so it's not a recent phenomena - I don't have a record of which year(s) were reported as poor air ones but it should be possible to check Met Office archives to see if there was a warm(er) winter in the run-up to the poor air reports.

Only partially true. Whilst it is the case that some caves have been known for bad air for a very long time, we have NO reports of bad air in G.B. from when it was discovered in the 1930s up until the year it had to be closed for this reason a couple of summers ago.

Whatever the cause is, something - changes in land use, changes in use of fertilizers, global warming, rise of fundamentalist religions, whatever - has changed on Mendip (I have not heard similar reports from other regions) in recent years.

Graham - we have had problems with CO2 levels in a number of Peak District caves/mines in recent years: Knotlow Cavern, Robins Shaft Mine and Water Icicle Close Cavern being among them. I don't now how things shape up historically but these problems have been occuring in recent years.

There is currently monitoring taking place in part of Knotlow Cavern to see if there is any connection with weather, farming activity, etc.

See the DCA website for more information.

 

[cap n chris]

Have any scientific test been done in Mendip caves to see if we have any unusual bacteria eating our walls.

Not to my knowledge. Are you on about extremophiles/dark life?

 

[Dep]

Some very interesting responses there, thanks for the info.

Cold air displacement theory sounds good as far as correlation with temperature goes.

Also intersting to look for correlations between sudden changes in air qaulity vis-a-vis agrigultural chemicals or changes on the catchment area of the stream.

The maths model question is interesting, unfortunately my differential calculus is horribly rusty and I have forgotten how to work it out into an equation. I suspect the true answer in practical terms is that it is academic, as soon as there is a noticeable problem (at much lower levels I guess) get the hell out of there.

Actually quite scary to think that a volume as large as the LDE (and presumably the approach area below it) could be so dangerous.

Ever heard of Lake Nyos in Cameroon?