Cal. Code Regs. tit. 8, § 7083 – Mine Rescue Stations.

(a) (4-67). Every mine at which more than fifty (50) men work underground at one time shall be provided with a mine rescue station located at or near the mine, or shall be a member of a cooperative mine rescue station located no greater distance from the member mine than can be covered by the most convenient means of transportation in 2 hours during any season of the year.
(b) At each mine in which the Division considers there is a serious hazard from mine fires or mine gases, the Division may require the installation of a mine rescue station, with apparatus and equipment as specified in Section 7084.
(c) (4-70) Smaller mines having 10 to 50 men underground at one time shall join a cooperative mine rescue station or shall have one man for each 10 underground employees or fraction thereof trained annually in the use of breathing apparatus.
It is recommended that small mines, regardless of size, affiliate with a cooperative mine rescue station wherever practical. Where it is not practical, each mine should have some man in its organization who is trained and qualified in the use of breathing apparatus, to accompany mine rescue crews into the mine in case of emergency. This man should be familiar with the mine workings, mine ventilation, water lines, electrical circuits, and underground hoists.
(d) Each rescue station shall be in the immediate charge of a competent and responsible man. The man in charge need not be employed exclusively at the rescue station, but his employment shall be arranged so that he, or a competent and responsible substitute, shall be promptly available in case of need.
(e) Telephone, or other equally rapid means of communication, shall be maintained between the residence of the man in charge and the rescue station and every mine affiliated with the rescue station.