Section 7980 Of Chapter 2. Gassy And Extrahazardous Tunnels From California Labor Code >> Division 5. >> Part 9. >> Chapter 2.

. All electrical equipment and machines, including diesel engines, used in tunnels or underground mines classified extrahazardous shall be permissible equipment. The division may, however, permit the use of nonpermissive equipment in a tunnel or underground mine in areas where it finds there is no longer danger from gas or other hazards.