Nettle Pot CO2 - Ann Soulsby/Alan Brentnall/Phil Wolstenholme
Present:
Ann Soulsby, Jess Eades, Richard Tooley, Phil Wolstenholme & Martyn Grayson
This was supposed to be a photographic trip for Tooley but bad air put a dampener on that. Martyn rigged followed by Phil and I was in third place. Managed to get down the extremely fast entrance rope without a hitch and made may way along the traverse to the top of Crumble and Beza. Going along the traverse I felt like I was out of breath and told Martyn that I was going back out. Martyn said that he and Phil were okay and it was probably my imagination. I rationalised this in my brain and sort of convinced myself they were right. After all although we have hit pockets of bad air before in Nettle it had always been right at the bottom.
I carried on and sat chatting with Phil – in the meantime Richard and Jess had joined us and my breathing settled down. Phil followed Martyn down Crumble and I went down next – at this point I started to worry again as I appeared to be once more struggling to breathe – not usual on the way down – so I called for Richard to join me. In the meantime Phil had set off down Beza. Richard confirmed my suspicions and decided to go straight back up the pitch. I shouted to let Phil and Martyn know that we would not be following. If I had nay doubts before I certainly did not have them when I was prusicking.
Once again the traverse seemed to be particularly bad on the way out. We all made our way out as quickly as possible.
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Re: Nettle Pot – Saturday 8 September 2012
Postby AlanB » Wed Oct 17, 2012 9:36 am
Extract from a report which I submitted to DCA today.
Last night (Tuesday 16/10/2012) along with Ade Pedley, Lee Langdon and John Martin, 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 to DCA as containing a high level of carbon dioxide. The meter used was DCA's Crowcon Gasman single gas monitor. Readings direct from the LCD display were noted - see below.
Sample Point % Carbon Dioxide
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 (alarms are set at level 1 = 1.50% and level 2 = 2.00%), 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 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 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.
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by Phil » Wed Oct 17, 2012 4:38 pm
Alan
Thanks to all of you for taking the trouble to do this, and it just shows how having accurate real-time data can make the situation much clearer to understand. And good to know what sort of percentages will cause the panting, etc.
Once I'd had a sit-down for a couple of minutes, I felt fine, but it's clear the exertions of SRT place a much higher demand on the respiratory system than ordinary caving or just hanging about, and so that should be borne in mind when descending deep, constricted pitches.
I think that's probably the problem with Beza Pot - it's just not very big (apart from vertically), and so the overall volume of fresh air available is quite low, especially if a few folks have already abseiled down, which will have probably pushed some air out the top (in a reasonably enclosed space, which it is), and put a fair amount of extra CO2 in (4% by volume on exhaling), which is then obviously still hanging around on the way back up. If it had been Titan, I doubt there would have been a problem, as the overall air volume available is massive, and the draught from other parts of the cave and the outdoors is far more pronounced too.
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by AlanB » Thu Oct 18, 2012 9:07 am
Actually Dan Lay and I both (independently) recorded quite high CO2 readings at the foot of Titan about a month ago - but I'm sure that one contributory factor in the Peak District CO2 problem is the low airflow in some caves. It is noticeable that caves with active streamways (Giants, Streaks, Carlswark, Peak, Speedwell) do not suffer, and stream flow must act as a pump. There are of course some obvious exceptions to this - Lathkiller Hall has a severe CO2 problem at the moment, despite a very active streamway, and, of course, the most CO2 polluted part of Knotlow seems to be the point where the sizable stream enters Waterfall Chamber - i.e. at the top of the pitch.
It's a very curious problem, which probably means that there are several inter-linked causes. But it's just another subterranean problem to add to all the challenges which we accept as part of the attraction of our sport. Cavers (especially experienced cavers leading novices) need to make sure that they are aware of current problems, they need to know the effects of low O2 high CO2 atmospheres on the body, they need to be aware of the problems these symptoms can cause and they need to have a plan for dealing with the issues when they arise.
As you say, Beza is an awkward pitch (certainly more likely to be called Bitch than its counterpart in JH!) and although I try to keep a certain level of fitness, I know that I will be breathing heavily while climbing it, even when the air is good. If you replace 2% of the oxygen with CO2, this will obviously increase the respiration rate, and not knowing the actual figures could cause anxiety and an even higher rate.