Asphyxiant gas in the mine

Exploring a district in the underground mine where asphyxiant gas level is high. We have some Drager gas detectors. At 2:50 mn, the first detector is shouting, telling us it's dangerous. There's not enough oxygen (16% oxygen, this is 50% the oxygen you need in a normal level, and very too much carbon dioxide). We are going more far than dangerous, that's why it's shouting hardly during all the recording. In fact, we try to reach some stairs, written on the map, in aim to climb to an upper level. It's not very distant from the tunnel where we are. It would means a better air, because carbon dioxide is heavier than air. Unfortunately, the stairs are too far for us, going there would means to reach a district where oxygen level is 14%. This kind of level causes death within 5 to 10 minuts, no more. It means we encountered a defeat and we can't explore an entiere district where there's an enormous stone crusher (written on the map as a gigantic machine). It's a bricolage recording (not very good), because we are in an extremely harsh conditions. It looks we are calm, it's because we are accustomed with this kind of situations, but it's hard for us. After this, we all had headache and throw up feeling. That's normal. Lack of oxygen was high. Above all, lack of oxygen is a common situation in the underground ore mine, that's why we use detectors.