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.
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