Craig In the olden days of coal mining - I mean way back in the olden days, back before electricity, steam engines, gasoline engines, etc, the days before all these modern conveniences - if a job required power, you had two choices: human power or animal power.
In underground coal mines, the human power came from men and boys. Women were thought to bring bad luck in underground mines, so they were not allowed. (This made them the lucky ones!) The animal power was supplied by dogs, cattle, goats and various members of the horse family.
Ventilating a coalmine was the biggest problem. Getting a large enough volume of fresh air to circulate through the mine workings was a real challenge. The movement of fresh air was needed to carry off the dangerous accumulations of explosive gases and coal dust that were emitted during the mining process. A lot of crude devices were used: huge bellows mounted on the surface, etc. There is only one word to sum up the ventilation in the mines in those days: poor. Today's mines are ventilated by large fans turned by high-speed electric motors. Still, once in awhile, there is a mine explosion, which kills coal miners. So, in the olden days, before any mechanical means of turning a fan had been invented, coal miners had a very hazardous job and their life expectancy was very short.
Mine fires, flare-ups and explosions were common, because of the pockets of explosive gases that accumulated throughout the workings of the mine. These pockets of gas were more likely to build up to dangerous levels when the mine was idle, overnight or during weekends. A lot of miners were killed in mine fires and explosions, when a pocket of gas would be accidentally ignited.
To cut back on the fatalities of the miners, the job of fire boss came into existence. One miner would be designated to go into the mine, to rid the working places of these bothersome pockets of gas. He accomplished this by carrying a lighted torch with him. Hopefully, any gas pockets he encountered would harmlessly be burned off. The few survivors of this task soon learned to wear several layers of wet clothing and wrap their faces and hands with layers of wet cloth. This precaution helped somewhat, but the fatality rate among these miners was extremely high. No other miners would be allowed to go into the mine until one of these miners had returned to the surface to give the all-clear signal.
To check for "black damp" (air with insufficient oxygen to sustain life) these miners carried a canary in a cage with them. If the canary died, the miner would turn around and run for his life. If he were lucky, he would make it back to the surface. If he didn't make it to the surface, the company would send in another wet miner, complete with torch and canary. They lost a lot of miners this way, but at least one miner at a time, instead of a whole mine full at a time.
Somewhere along the way, the name fire boss was given to these heroic miners and the name stuck. There still are fire bosses today, and they still go into the mines to look for pockets of explosive gases and other dangerous conditions, and they still must report to the outside that all is clear before any other miners can enter the mine. Their chances of survival are at least a thousand times better than their old-time counterparts, and no, they don't carry a lighted torch or a canary in a cage, and they get to wear dry clothes, thank goodness.