The time of commencement and closing of a worker's hours of work in any undertaking shall be fixed by the rules of the undertaking concerned subject to the following:

(a) in the case of operations underground, work commences when the worker enters the cage or lift to go down and ends when the worker leaves it at the surface; and

(b) in the case of operations underground, where the work place is reached by going down a gallery, the hours of work is reckoned from the time when the worker enters the gallery to the time when he or she leaves it at the surface.