Coal bed gas is a kind of burnable gas without any color, taste and smell. It will explode if the concentration ranges at 5%~16%, and if oxygen larger than 12%, it will also explode when meeting the naked light or temperature between 650 ℃ to 750 ℃ . Explosive power will be the biggest if concentration is 9.5%. It will not explode if concentration larger than 16%. It was generated by coal or rotten plants and exist in two states: absorbing and dissociate. China is the third biggest coal bed gas reserves country. Generation with coal bed gas not only keep the mine safe but also remit the situation of lacking power.