Lathkill Head Upper Entrance - Alan Brentnall
In response to a report of high CO2 levels in Lathkill Head Upper Entrance, a small group of us (Ann Soulsby, Christine Wilson, Andy Chapman and me) descended the cave, and, using the DCA CO2 meter, Ann measured the atmosphere at various locations. The following was reported back to DCA.
Foot of rope in Waiting Room: 1.55%
Top of choke at the bottom of Waiting Room: 1.70%
Inside the choke between Waiting Room and Lathkiller Hall: 2.00%
Lathkiller Hall: 1.61% - 2.31%
The air in centre of Lathkiller Hall felt to be moving slightly, and this is where the lower readings were recorded; the higher readings in Lathkiller Hall were taken in the boulders nearer the stream, where there the air was still. There didn't feel to be much air movement in the choke either, and, of course, the extra exertion of climbing through the choke would amplify the effects of CO2, and the lower levels of oxygen.
This particular cave has been subjected to high CO2 readings in the past, particularly when the lower reaches are sumped, as they are at the moment.
While it's difficult to make any recommendations (cavers need to assess the effects of these atmospheres upon themselves) we have experienced much higher concentrations of CO2 in the Walf-Knotlow system without any long term ill effects, and you would expect the duration of any trip into Lathkill Head under the current sumped conditions to be much shorter than a trip into Walf-Knotlow.
Some further thoughts and an explanation from Christine (all temperatures are Celsius, and assumes the cave temperature to be around 9 degrees C):-
Looking at the records, open air temperature has been over 9 degrees a.m. and p.m. in Castleton during August and September. October was also rather warm, with the lowest average temperature being 8 degrees. In November the lowest average was 5 degrees, and only dropped below 5 degrees at night on 10 days, so this was also quite a warm month. And all this warmness may explain a bit of stuck CO2 ….
If it is 9 degrees and over, night and day, and if this is fairly consistent, then we can expect CO2 to be kept at source and build up a little. A few nights where the temperature drops well below 9 degrees seems to help help air/CO2 to move by convection around and out of the cave.
It's all predictable, and we can keep an eye on historical weather data and daily max and min temps by using (for example) http://www.accuweather.com/en/gb/castleton/yo21-2/august-weather/329172?monyr=8/1/2014&view=table