Serious CO2 problem in Nettle Pot

Nettle Pot - Serious CO2 problems

There are currently very serious CO2 problems in Nettle Pot.  It is suggested that cavers stay away until further notice.  A warning notice about the problem has been hung from the bolts immediately under the lid.

Jenny Potts
DCA Secretary

Anyone know anything else about this? Purposefully measured and detected, or someone unfortunate enough to encounter it whilst on a trip?

Just curious I guess.

Not really measured as such - Martyn Grayson and I went down to the beginning of Red River Passage two weekends ago, and encountered a very stuffy situation, sufficient for us to head back up more or less immediately. Beza Pot was hard work, and we assumed that the problem was either high CO2 or low O2 - either way, there wasn't much of a draught down there apart from at the small junction chamber that leads to Hell, but it wasn't strong enough to feel good about. I assume that word must have got around, as I've not been down there before, so had nothing to compare it with. But from other comments I've heard, Beza can often be difficult on the return journey.

By the time I got back to the base of Crumble Pot it was better, and once at the top of that, no problems at all, so it was definitely from Crumble downwards that it was a bit thick...

We had also reported similar 28 july, though further up. not been back since, sorry if this isn't very helpful, O.G.

I was on the trip with og and can confirm the pretty awful situation. This extended from the base of Elizabeth through the sting and into crumble and beza. Gutted really as I was thinking of a trip to dratsab. Let's hope it sorts itself out. 

I've heard rumours that an open-mesh lid might be fitted soon, at least to try and get some circulation going - it could help. I was so attuned to the stale air that by the time I reached the Elizabeth pitch head, I swore I could smell the grass outside. I assumed this was just wishful thinking, but it turned out two of our party had already gone out, specifically to open the lid, and were sat at the top chatting.

So maybe an open mesh lid, over time, would provide the pressure difference to get things moving - the draught seemed to be coming up the passage from Hell - I've never been down there, but I assume it's tight. So where would that draught come from exactly? I've now seen a plan of the lower part of Nettle, so now know what the orientation is exactly of those passages relative to the main chambers (it did feel like the opposite direction), but that end of the system is nearest Oxlow, and the horizon close to the level of the floor of West Chamber. Looks like a heck of a distance to close though.

Hell is intermittently tight, and the tight bits are more technical than tight, but, in between, there's plenty of room. I've always thought that Hell gets a good draught, as oppose to the Red River which doesn't seem to.

The current CO2 intrusion is affecting many more venues than Nettle, and, presumably, has something to do with the persistent low-pressure climate this year, and I would have thought that a general warning to cavers in the Peak to cave with caution (and a meter if you can) would have been more appropriate than highlighting a single cave where measurements have yet to be taken.

al said:

The current CO2 intrusion is affecting many more venues than Nettle, and, presumably, has something to do with the persistent low-pressure climate this year, and I would have thought that a general warning to cavers in the Peak to cave with caution (and a meter if you can) would have been more appropriate than highlighting a single cave where measurements have yet to be taken.

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There is now a general warning on the DCA web site:- http://thedca.org.uk/ You only have to mention these things to the appropriate people. 

Regards, Mel.

Forums and the internet are a great form of communicating potential issues like this.

Can I please just ask that people at least consider the potential implications to posting things on here. A number of venues have been shut down in the last few years based on reports with varying degrees of reliability, and I don't want this to be unnecessarily increased. Once a cave is shut, it can be hard to get it open again, even if the air is now fine down there.

My suggestion would be to alert the DCA of all bad air experiences, to send any meter readings to them, but only put a small notice on here about when and where if deemed very important. The DCA can digest the info and then conduct the appropriate response...

Rob said:

My suggestion would be to alert the DCA of all bad air experiences, to send any meter readings to them, but only put a small notice on here about when and where if deemed very important. The DCA can digest the info and then conduct the appropriate response...

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I agree totally. I have carefully worded the warning and not mentioned any specific site, etc. Tell DCA about any problems, that's what they are there for and can they then investigate and report back appropriately...

Good work Mel 

Yeah, that's partly why I hadn't mentioned it here until now, as I was trying to find out if there was any other data available - and also one bad day doesn't prove much, unless it's corroborated elsewhere. A few discussions have led to a conclusion that 02 meters might be a useful addition to regular trips in the area though, if only to provide more data to feed in to the equations.

Thanks all for the info.

As I said, I was just curious as to how the DCA warning (17th September) came about.

Understanding the basis of the warning can be useful information in making a decision where/when to visit a particular site, general area, or region. For a general example, my decision making would be different, if I knew that deadly high meter readings were take in an entrance shaft over a long period of time, or knowing if only a short section was affected where people found breathing heavy, on a single a trip. In the first instance, this would clearly be a definite no-no! But I'd also have another peice of information which I could use to weigh up the CO2 risk at nearby venues. In the second instance, knowing this information would perhaps avoid a knee-jerk from the non-caving community, but still gives us the important information we need (e.g. we could choose to avoid the sections affected).

Totally agree with comments made by all. 

Has anybody been down here since the warnings came about? Had a really fun trip down Maskhill on Thursday night and looking for something for tomorrow in the area.

global_s said:

Has anybody been down here since the warnings came about? Had a really fun trip down Maskhill on Thursday night and looking for something for tomorrow in the area.

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On Tuesday 16/10/2012 with three other experienced cavers, and having notified DCRO's duty controller and a reliable callout person, I carefully descended Nettle in order to sample the air quality which had been previously reported as containing a high level of carbon dioxide. The meter used was DCA's Crowcon Gasman single gas monitor, and sampling was done continuously, hoping to use the logging feature of the instrument. Readings direct from the LCD display were also noted, and these are shown in the table below.

Surface 0.01%
Top of Gulley Pitch 2.08%
Foot of Gulley Pitch 2.22%
Top of Crumble 2.31%
Window to Beza 2.34%
Foot of Beza 2.41%
Foot of Shakes 2.37%
Foot of Fin Pot 2.47%

The Gasman started alarming at the foot of the Bottle Pitch, and, while descending the pitches down to base of Fin Pot, the air quality slowly deteriorated by around half a percent, but not to a dangerous level. The effects, however, were very noticeable when returning up the pitches, when symptoms similar to working at altitude were noticed - panting etc. However, having access to the meter readings, and seeing that the levels were not dangerous was reassuring, and the return journey and de-rigging was done without any major problem.

My personal conclusion looking at the readings taken on the trip is that the levels of carbon dioxide in Nettle are now not sufficiently high to cause major concern, they are considerably less than Lathkill Head upper entrance, and the latest passage discovered in Water Icicle Close Cavern.

But cavers do need to be aware that there is currently a general problem with higher than normal concentrations of carbon dioxide in some Peak District caves and mines. Cavers need to know the symptoms, the likely problems and have a preformed plan when visiting any cave in the area.

Ideally cavers should carry an oxygen meter - these are certainly cheap enough for caving clubs to purchase nowadays.

As winter approaches, and temperatures drop, we should expect to see CO2 levels decrease in caves. Knotlow, a much better ventilated system than Nettle, was already back to normal last week.

If any body drops Nettle (especially Beza and Crumble) in the next few weeks, please drop me an email and let me know your experience - gasman@theDCA.org.uk

Cheers
Al

Cheers Al, think I'll go and have a look down there then!

I've just added a link to Al's post to the DCA web site. Thanx for the report! 

Regards, Mel.

Good work Al. Would be interesting to repeat after some proper cold weather

al said:

Ideally cavers should carry an oxygen meter - these are certainly cheap enough for caving clubs to purchase nowadays.

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Just as a small point - an oxygen meter will only tell you what the oxygen level is - CO2  and other gases can still be present at dangerous levels with normal oxygen concentrations, it just depends on what gas has been displaced. Even if you have an oxygen meter reading normal levels, if you are getting symptoms of bad air, the most sensible course of action is to leave.

Brendan said:

Just as a small point - an oxygen meter will only tell you what the oxygen level is - CO2  and other gases can still be present at dangerous levels with normal oxygen concentrations, it just depends on what gas has been displaced. Even if you have an oxygen meter reading normal levels, if you are getting symptoms of bad air, the most sensible course of action is to leave.

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Brendan, you're absolutely correct in saying that the best advice in the presence of any bad air is to leave the system.

However, this is not what tends to happen - people can and do carry on caving in atmospheres containing quite debilitating levels of CO2, and I think that cavers need to be aware of the symptoms and the problems that may ensue if they do carry on caving - particularly in the Peak District where this problem seems to be most prevalent.

You?re also quite right to point out that an O2 meter may indicate values which look OK in the presence of toxic levels of other gases, but so far (fortunately) we have found that O2 depletion does correlate with CO2 increase.

And I would recommend an O2 meter simply because they are affordable, and an O2 meter is far better than no meter.

If Derbyshire is so bad wouldn't it be an idea for all Derbyshire clubs to get a meter? What is DCA doing apart from sending out warnings. We can't just keep restricting access because fat lad got out of breath coming out a cave/mine :ang:
If we keep restricting access then i'm going to have to spend more evenings and weekends at home with her and the kids so SORT IT OUT