MSHA - Code of Federal Regulations - 30 CFR 57.22235
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MSHA - Title 30 CFR
30 CFR § 57.22235
Actions at 1.0 percent methane (I-C, II-A, II-B, and IV mines).


(a) If methane reaches 1.0 percent in the mine atmoshpere, all persons other than competent persons necessary to make ventilation changes shall be withdrawn from affected areas until methane is reduced to less than 0.5 percent.

(b) If methane reaches 1.0 percent at a work place and there has been a failure of the main ventilation system, all persons shall be withdrawn from the mine.