POOR AIR, SUMMER 2005

[cap n chris]

Poor Air on Mendip

Reports of poor air in some Mendip caves leads to this general alert.

Extremely poor air has been noted in Honeymead Hole - the cavers managed to get to the surface but once out took half an hour to recover.
(It is highly likely that Little Crapnell Swallet will also be affected).

Poor air has also been experienced in Swildon's Hole and in Wookey Hole beyond the showcave (divers section).

Other sites where poor air may be experienced:

GB Cavern
Manor Farm Swallet
Tynings Barrow Swallet
White Pit
Cuckoo Cleeves

It would be appreciated if cavers visiting any of these sites report any instances of poor air during the summer months so that the situation can be monitored - it should be easy to do so by using this forum.

Many thanks,

CSCC Conservation & Access Officer.

 

[badger]

had trips down reads cavern and swildons (very short trip, in wet out short dry)
did not find any problem with air quality in swildons.
However reads has a dead animal nicely decomposing right hand end of main chamber

 

[cap n chris]

When?

 

[cap n chris]

It is not uncommon to hear of cavers reporting that "nothing seemed to be wrong when we went there the other day" but this does not automatically mean that everything is OK. Some people are more attuned to poor air than others and degrees of observation alter accordingly. Put simply, some people notice stuff that others don't.

Although people may find themselves breathing a bit harder when caving and putting it down to being less fit than they reckoned, or just because of the exercise they're getting, it is worthwhile making observations of the conditions - this has been done over the last 2-3 weeks with regular flame tests in various parts of the cave. The conditions have steadily declined, despite some heavy rain, and the latest observations taken are:

Monday 11th July: air test trip. In wet way - air noticeably poor from the start; quite laboured breathing by the time we reached Water Chamber. Flame test - match lit and candle lit but flame quite small at around 1cm high - it would go out if the candle was moved from side to side.

Beyond 20': another flame test - first match went out but second managed to light candle; similar result to above.

Below Tratman's Temple: matches would not light at all.

Just before sump 1: only half the flammable bit of the match head lit before it extinguished - so immediately headed out. Heavy breathing, light headed and headaches continued until exiting cave. Breathing returned to normal within 3-4 breaths on the surface. Headache persisted for half an hour or so.

 

[badger]

weekend of 9 & 10 july, it was a very short trip down swildons only going as far as water chamber, did not notice any problems, but as you have stated different people pick up on bad air quicker than others, and had we gone further perhaps we would have picked up on the bad air, short trip only because of time needed to get home from mendips 160 miles away, there was 2 cavers who went in with us who where going to do the round trip so not sure how they faired.

 

[cap n chris]

CARBON DIOXIDE TESTING RESULTS
SAMPLES KINDLY TAKEN BY DR. A. BOYCOTT
Thursday 14th July 2005, all taken during afternoon 2:15pm-5:00pm


Site, Location, CO2 measured

GB Cavern, Dry Way/Gorge junction, 1.5%
GB Cavern, Below Ladder Dig, 2.5%

Swildon's Hole, Water Chamber, 1.75%
Swildon's Hole, Top of 20', 2.25%
Swildon's Hole, Below Tratman's Temple, 2.1%
Swildon's Hole, At sump 1, 2.0%
Swildon's Hole, Old Grotto (top end), 2.0%

Comment: CO2 levels around 2% cause noticeable laboured breathing under exertion but on resting composure returns readily. If you or anyone in your trip, while visiting either of these sites, experience difficulty breathing you may wish to reconsider your trip/route in the cave.

 

[graham]

Of course what the Cap'n has failed to tell you is that hazards on that trip (the Swildons one) did not come from CO2 but from faulty tackle & poor techniques ...

 

[paul]

I've posted this link before with regard to high CO2 levels in Knotlow Cavern, Derbyshire but its worth posting again.

Have a look at CARBON DIOXIDE, CAVES and YOU

 

[cap n chris]

Of course what the Cap'n has failed to tell you is that hazards on that trip (the Swildons one) did not come from CO2 but from faulty tackle & poor techniques ...

Ooh, you bitch! It was only a VERY MINOR epic.

Actually, Graham, I expect your Mate, "the Boy", failed to say that when he approached the ladder I specifically offered to lifeline him (as it was already rigged for the return) but he said, "I'm not bothered" so off he went. Mind you he didn't get far - from the sound of things, I expect he told you what happened.

Anyway, we managed to cobble together a workable ladder from the broken bits and thankfully managed to get out. Not surprisingly, though, the lifeline was used on the second, successful, attempt at getting up and out.

A good example of why YOU SHOULD ALWAYS USE A LIFELINE ON ALL LADDER PITCHES; the ladder was only 3 years old. So, off to Uncle Tony's in the morning to shell out £140 on a new death trap.

 

[cap n chris]

Thanks for the link, Paul. I've got a PDF of that already but it is perhaps worth reiterating one of the final comments which states that if one experiences any symptoms of foul air underground one should cease the trip and head for the surface.

We know that the air in GB Cavern and Swildon's Hole is presently foul but one doubts whether a course of action (or prohibition of visits) is going to be put into place unless the CO2 reaches or exceeds 3%.

 

[Caversam]

Probaly a bit late now, but was in Little Crapnell Swallet on the 18 of 5 and ran into sum really bad air. I think (Bad removed brain cells) it was just below you get low down to enter a duck. Took about an hour to get rid that dam head ache.

The guy I was with noticed it a while before, but didnt think to tell me.

Sam

 

[cap n chris]

Received a report from SMCC members that CUCKOO CLEEVES has very poor air in it at present (7th August 2005).

 

[cap n chris]

Add Rod's Pot to Cuckoo Cleeves (above).

 

[mudmonkey]

Rod's??? that's intriguing with no water - anyone got any ideas on the sources for this CO2? Presumably nothing can get washed in and rot???

Where's the poor air?

 

[Dave H]

Rod's??? that's intriguing with no water - anyone got any ideas on the sources for this CO2?

Surely, it's such a classic that it gets dozens of visitors every weekend all breathing out the stuff? :wink:

Without water movement to provide air currents in bottle shaped caves like Rod's is there any method for the CO2 to 'dissappear' or will it just get higher in concentration? Or are the external atmospheric variations enough to clear out the CO2 even from the bottom of caves?

 

[Andy Sparrow]

Rod's???

This surprises me. Does this information come from a reliable source?

 

[cap n chris]

Roxanne's party experienced it.

It looks like I might need to go and visit just to double check! However, let's assume that the air there is indeed bad.

I'd like to get feedback from others on reasons why you believe bad air may exist in UK caves. After some thought here are my best guesses:

Wet caves:
Low water levels mean less fresh air is "dragged" in
Low water levels mean less vegetation is cleared away, allowing it to rot and add to the CO2
Low rain fall means the water which is percolating through cracks into the cave has more time to become acidic (fulvic/humic) before it reaches voids and therefore reacts more vigorously before effervescing out CO2
Low water equates with (usually) good weather and higher temperatures meaning that there may be less differential between the ambient temperature of the cave versus outdoors resulting in less natural "breathing" which may otherwise clear out CO2
Other possible CO2 sources:
People (cumulative effect - I guess there more trips in summer than winter?)
Manure/fertiliser washing in (cows kept indoors during winter)
Thousands of seeds being washed in (etiolation and subsequent rotting)

Dry caves:
Less temperature difference resulting in less natural "breathing" of the cave resulting in higher CO2 is about all I can think of. While Rod's Pot is a dry cave it is one of the steepest Mendip sites, with a dip of around 70 degrees hence meaning it is an ideal "collecting hole" for CO2. Also, if it is visited by outdoor groups the cumulative build up effect would be noticed during summer, I guess.

N.B. We know that Mendip and Derbyshire are affected more by poor air than elsewhere so perhaps the dip of the limestone is the additional dynamic which aids the build up of CO2 in these regions as against S. Wales and Yorkshire. Also worth considering are the multiple entrances to many Yorkshire caves which would create through-drafting which aids ventilation (and OFD).

 

[paul]

N.B. We know that Mendip and Derbyshire are affected more by poor air than elsewhere so perhaps the dip of the limestone is the additional dynamic which aids the build up of CO2 in these regions as against S. Wales and Yorkshire. Also worth considering are the multiple entrances to many Yorkshire caves which would create through-drafting which aids ventilation (and OFD).

However, in Knotlow Cavern in Derbyshire, one of the systems most affected by high CO2 levels, we have puzzling causes and efects. There is a logbook kept at the foot of the Climbing Shaft to record comments on air quality (see DCA Home Page and a PDF of the current issue of "The Derbyshire Caver" linked from DCA Publications which has some articles on the problem).

The system is relatively flat so dip of limestone can be disregarded and has many shaft entrances. Even changing shaft lids from solid metal to grills to improve ventilation doesn't appear (so far) to have an effect. The only thing that is almost certainly having an effect is that it is located under pasture and farms.

 

[cap n chris]

Thanks for your input, Paul. I imagine that even within distinct caving regions there will be caves with their own specific foibles which lends them more prone to bad air and it will be up to those based locally to come up with the best ideas of what is causing the specific problem at each location. I'm trying to work out a comprehensive list of different dynamics any one or combination of many which could lie behind poor air in different caves.

For instance, with Rod's Pot I do not recall whether there are any active "leaks" in the walls whereby higher acidity water could be gaining entry and creating CO2 as the usual solutional byproduct and need to visit the site to check whether this, perhaps in combination with the dip and the popularity of the site, could be why a dry cave has had the problem reported; on Mendip the problem is not limited to wet caves with White Pit amongst others being notorious for bad air and I imagine this could be the case elsewhere.

It would be good if BCRA or a scientifically minded person would like to engage in a long term study of the possible causes and mechanisms behind these apparently cyclic events; certainly it's a "warm weather" event and the Cold Trap theory (Gunn 2004) seems to fit quite neatly (I just looked it up)*.... actually this theory fits well with Rod's Pot.

Cold Trap theory summary: Imagine a single entranced cave on dipped limestone with the entrance higher than the body of the cave (i.e. a "downhill" cave rather than an uphill one). During Winter cold external air flows into the cave entrance by gravitational drainage and displaces the warmer cave air, causing it to return upward and flowing out of the entrance; thus a convection "breathing" effect is created and the air within the cave is good and fresh.

During Summer when the external air temperature is greater than the temperature of the "ponded" air within the cave, any convectional breathing only occurs at the uppermost part of the cave since the inner "pond" of air is considerably cooler than the external air thereby capping the cold air within; this reserve of cool air can be breathed for a while and exhalation will increase the relative levels of CO2 (which is also heavy); it's only when Winter returns that the whole system is "flushed" through again by the relatively colder air (now that the "cool" air within the cave has warmed to match the temperature within) flowing back in again. This is a neat theory.

At Knotlow there may be other stuff happening (I'm not familiar with the site). Consider: variation in barometric pressure, direction of external wind pressure and external air temperature in relation to internal climate. Relative volume of chambers and their location within the system could also play a major part.

 

[andymorgan]

I like this 'cold trap theory'. I'm suprised it was only published in 2004, it is quite an obvious explanation. I agree with Capn that it is a good theory for Rod's Pot. To get an idea of how much heavier than air CO2 is. You only have to look at B movies with steaming potions, with the 'steam' flowing DOWN the sides of the glasses. The steam is dry ice (frozen CO2) turning back into gas.
If it visited by many people (like Rod's Pot) than people just breathing will increase it. The normal CO2 concentration outside is 0.03% exhaled air contains 5% CO2. With lung capacity of a few litres (don't know off hand) and a small cave voume it is easy to see how it can increase. It would be interesting to see if CO2 levels increase with depth.
I'm not too sure how a place like Cuckoo Cleeves can build up CO2 (who would like to visit that s***hole!) Perhaps it is decaying organic matter. I think the most interesting cases are the wet caves, you would have thought there would be more of an air current with the movent of the water, and although it may contain organic matter.
Perhaps it may be microbe action within the cave and in the soils above, maybe even air pressure may be a factor summer = high pressure, high pressure is sinking air if I recall correctly.