Cal. Code Regs. tit. 8, § 6981 – (15-5). Safety Belts and Life Lines.

(a) Safety belts and lines shall be worn when men work where there is danger of falling.
No employee shall be permitted to enter any bin, bunker, or other storage place containing materials which may cave or run unless he is provided with and is wearing a safety belt with life line attached. He shall be attended by another workman, who shall keep the life line reasonably taut at all times.
(b) Life lines shall be of three-fourths inch diameter Manila rope or equivalent.
(c) Life lines subject to excessive fraying or rock damage shall be protected or shall have wire center rope. Seriously worn or damaged rope shall be promptly removed from service.
(d) Safety belts and life lines shall be inspected by a qualified person before each use. When fiber ropes show serious abrasion, broken fibers, cuts, fraying, or other defects, such defects shall be reported to the person in charge.
(e) When in use, the life line shall be secured so as to prevent it from being accidentally loosened or dislodged.
(f) Safety belts shall be of a type approved by the Division.