生活中我们有这样的常识，在一个密闭的空间中当可燃气体达到一定浓度时，遇明火会立即发生爆炸，即剧烈燃烧瞬间蔓延至整个空间。而爆炸极限指在空气中，可发生爆炸的气体比例区间-In life we have such common sense, in a confined space when the combustible gas reaches a certain concentration, the event of fire will immediately exploded, that is, the spread of severe burn instantaneously to the entire space. The explosive limit means the air, the ratio can be an explosion of gas range