Reminds me of a trip that formed part of my introduction to the wonderful world of caving.
It was part of a 'managerial' type course that used the outdoors as part of the classroom.
Trips included trying to survey Richmond Copper mine, abseil Buttertubs, visit Crackpot and the trip in question to Windegg Mine Caverns.
We were told of the possibility of bad air, as the only smoker present at the time, I was instructed to use my lighter to test the air as per previous post.
Only trouble was, I was just under 6ft tall and so was raising and lowering the lighter down to just below my neck and all seemed fine.
After a chunk of time one of the team who was a little over 4 foot tall was complaining of shortness of breath etc. Taking the lighter lower showed the problem.
A rapid exit was made and all was fine, with a lesson learned.