Apparently, it was not the engineers or managers (I am sure there were managers even in those days). The sculpture in the rock salt shows the job that paid the most. These were folks who would try to detect the presence of flammable gas and burn them away. They would crawl on the floor with a fire held high. The leaking gas would be detected thus and they had no option but to wait and burn it off all. Once in a while, they would lose their lives to an explosion. Which is why the premium in their pay!