Labor Code § 7973
CHAPTER 2. Gassy and Extrahazardous Tunnels
In any tunnel or underground mine classified as gassy, all employees shall be informed of any special orders made by the division following an inspection. Such notice shall be given before entering the tunnel or underground mine. A copy of any orders subsequently written by the division shall be posted and all employees shall be notified at a safety meeting called by the safety representative before they are permitted to start work.