You must use a respirator if the fuel-gas concentration in the work area is 5% more than the lower explosive limit (LEL).
如果工作区域的油气浓度比最低爆炸浓度高出5%，必须使用呼吸器。
The paper experimentally studied the explosive limit and the critical oxygen concentration of several kinds of gases that are found in the mine.
通过实验，对煤矿井下存在的多元混合气体的爆炸极限和临界氧浓度进行了分析和研究。
According to the range of lower explosive concentration limit, methods for how to set up warning region were research.
通过分析氨气扩散后爆炸浓度下限范围，探讨了如何设置警戒区的方法。
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