# The Coal and Other Mines (Ventilation) Order 1956, Paragraph 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.

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Source: https://www.legislation.gov.uk/uksi/1956/1764/schedule/FIRST/paragraph/18 (the official version)
Page: https://openlegislation.uk/coal-and-other-mines-ventilation-order-1956/schedule-FIRST/paragraph-18
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.