This is most certainly not a normal workplace hazard. This Chinese incident was in a gold mine where methane is virtually unheard of. Where it does exist Methane can be lethal but in the lack of this gas , I can only theorize a premature detonation of explosives..... which is usually caused by carelessness. The Chilean incident was VERY unusual in that whole sections of the mine collapsed. This would have been very poor management attempting to reach an extraction ratio without leaving adequate pillars to support on gong activities..