Bad Air

crickleymal

New member
We were exploring an old mine in the Forest of Dean last night. We'd had a brief look at it last year and having got the owner's permission went to have another look. Someone is already digging a passage there which might connect to Sling Pit and they had encountered bad air down there

We had not got more than 25 metres in and no more than 3-5 metres down when one of our party questioned the air quality (not helped by the amount of sheep sh1t in the entrance chamber). So I asked him to try his lighter. It (a Zippo) refused to light. I could see the spark and smell the fuel but it didn't light. So we back tracked and it eventually lit right by the entrance. After that it lit every single time even in a breeze.

So my question is, what mixture of gas would prevent a Zippo lighting? I would have expected it to light down to about 15% O2 or thereabouts.
 

Bob Mehew

Well-known member
Thanks Duncan for the web site reference.  I would quibble with the claim "In fact humans can survive in an atmosphere containing 10% oxygen, so when the flame test just fails it is still measuring an atmosphere containing enough oxygen to survive".  Whilst yes a person might survive with 10% oxygen, if the missing 11% (21 - 10) has been replaced by CO2 then that level of CO2 will have a significant impact on a person.  One must be very careful about what might replace the oxygen.  For example, the recent DCA newsletter, the Derbyshire Caver No 145, contains an article on monitoring cave atmospheres and reports finding CO (not CO2) levels at above 2000ppm / 0.2%, a very disturbing finding!
 

PeteHall

Moderator
So when you need diving kit to get a cigarette to light it's time to turn back?
 

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maxf

New member
PeteHall said:
So when you need diving kit to get a cigarette to light it's time to turn back?

No ! It just probably means you should consider giving up smoking !
 
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