Section 7960 Of Chapter 1. Tunnels And Mines From California Labor Code >> Division 5. >> Part 9. >> Chapter 1.
7960
. In any tunnel or underground mine classified as potentially
gassy, tests for gas or vapors shall be made prior to start of work
at each shift. If any concentration of gas at or above 10 percent of
the lower explosive limit is recorded, the division shall be notified
immediately.