Yes, this is so. I suspect that one of two things happened.
1) the compressor ran out of fuel and they poisoned the air before they knew it.
2) the compressor was pumping its own fumes down into the hole...CO2 goes low i believe and that is what killed them.
Many ambar miners die the same way or in cave ins...Heck look at the US just thisyear in "modern" mines..
HB
