Coal Mining below ground is a most dangerous job. All Coal Miners know this each time they enter a mine and get on the portal bus. Coal Miners know there can be explosions and or collapses of the tunnels.
The Coal Miners work in teams and they work together using techniques that they have been trained for. They carry with them some life support systems with limited ability to sustain one for a brief time, hopefully long enough to find good air or a ventilation system.
They will work together as a team and get into a safety box if one is nearby. They generally get themselves secure and in a place with "good air" and then wait for the rescue team to come and get them out or make contact with them.
Each company has certified rescue teams on-call and ready to go in the rare event of such a potential eventuality or catastrophic horrific situation.
I propose an additional coal miner rescue system in each safety box, which would be used in case the Coal Miners are completely out of oxygen and surrounded by only poisonous gases such as Carbon Monoxide, Carbon Dioxide or other gases. This additional system would have in it hydrogen sulfide gas.
The hydrogen sulfide gas would be taken as a last resort, which could be breathed in and thus set their bodies would be lowered to only 10% of their normal.
This would give them 10-times the length of time until the rescue and thus improve their chances of survival during that critical time needed to dig them out or mount a rescue from another adjacent tunnel. Think on this in 2006, as this could be a great invention.