18.—(1) There shall be provided and maintained in connection with every ventilating fan driven by mechanical power (other than an auxiliary fan) a water gauge and either an automatic indicator registering the number of revolutions of the fan or an automatic indicator registering the ventilation pressure.
(2) The manager of every mine shall give directions as to the speed at which any machinery driving such a fan is to be run to the person in charge of that machinery.
19.—(1) The person in charge of the machinery driving such a fan shall examine the machinery and observe the water gauge and automatic indicator at intervals not exceeding—
(a)in the case of a mine in any part of which the use of lamps or lights, other than permitted lights, is unlawful, a half hour or such longer time as an inspector may approve by notice served on the manager;
(b)in the case of any other mine, two hours.
(2) Where an automatic indicator registering the ventilation pressure is not in use the person in charge of the machinery driving such a fan shall at the end of each period of two hours enter in a book provided for the purpose by the owner of the mine the number of revolutions of the fan and the pressure shown by the water gauge at the end of that period.
(3) The person in charge of the machinery driving such a fan shall forthwith report to the official of the mine under whose direction the works—
(a)any damage to or defect or derangement in or stoppage of that machinery; and
(b)any unusual variation in the pressure shown by the water gauge.