CFR /  Title 30  /  Part 57  /  Sec. 57.22602 Blasting from the surface (I-C mines).

(a) All blasting shall be initiated from the surface after all persons are out of the mine and any connecting mines.

(b) Persons shall not enter the mine until a competent person has examined the blast sites and methane concentrations are less than 0.5 percent.