Section 7961 Of Chapter 1. Tunnels And Mines From California Labor Code >> Division 5. >> Part 9. >> Chapter 1.

. The division shall investigate immediately any notification of a gas reading 10 percent of the lower explosive limit or higher by an employer in a tunnel or underground mine classified as potentially gassy. If the inspection determines the likelihood of encountering more gas or vapor, the division may halt operations until the tunnel or mine can be reclassified.