Internet knows much, but not all. It seems that the only fatal caving accident in the Southwest in the last 10 years involved a chap lowering himself into a mine shaft. He was a responsible guy; he was aware of the potential dangers of bad air in such spaces, so he had brought a gas meter. If such a device detects undesirably low levels of oxygen, or high levels of detrimental gases such as carbon monoxide, it kicks up quite a racket with beeping and ominously flashing lights.
It seems that this chap had lowered himself a bit too fast - between the moment of the alarm going off and the moment he had stopped his descent he had already reached the bad air with his head. And he did try to turn around on the rope, and climb out of it, but a change-over is a bit fidgety, and he didn't make it. Most sad.
I can't find an account of this accident anywhere. My knowledge of it may be flawed. But it does illustrate a point: bad air does occur underground, and one should be careful with it. The cave rescue team has a few gas meters, and we should know how they work. We had two new ones, and we used part of a Thursday training evening to practice with them.
The last time we practiced with them someone held one near the exhaust of Rick’s Land Rover. Rick then started the engine. Without any delay the alarm went off. This time I paid a bit more attention to why exactly; the highest reading I saw was 421 ppm CO… for reference: a USA working place can have 50 ppm max. So don’t bring your car down a cave. It’s not good for you.
One of our rescuers smokes. He put his own breath to the test; he took a deep nicotine breath, and took his time breathing out onto the gas meter. Yes the alarm did go off. It seemed to be worse than Rick’s car… some people pay money for strange sensations.
Next week we’ll bring one down the next trip venue. It’s only a small adit, and if we are with enough people we may exhaust the oxygen in there. We will be able to monitor that most precisely! And whether I got the story of the unlucky guy precisely right or not; the story serves its purpose on reminding one a gas meter is only of use when used in the proper way…