Before charging and blasting in gas tunnel, safety inspection must be done to ensure the gas density less than 1%.

瓦斯隧道装药爆破前必须进行安全检查，确保瓦斯浓度小于1%。

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Before charging and blasting in gas tunnel, safety inspection must be done to ensure the gas density less than 1%.

瓦斯隧道装药爆破前必须进行安全检查，确保瓦斯浓度小于1%。

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