# The Coal and Other Mines (Locomotives) Order 1956, Paragraph 30


(1) No person for the time being operating any diesel locomotive in a mine shall keep the engine running when that locomotive is stationary except—
(a) during brief halts while the locomotive is in use; or
(b) while the locomotive is being tested.
(2) If at any place in a mine in which a diesel locomotive runs there is found in the general body of the air an amount of carbon monoxide exceeding 0.005 per cent. by volume, the manager shall forthwith take such steps as are necessary so to improve the ventilation at that place that that percentage of carbon monoxide is not exceeded.
(3) If at any place in a mine in which a diesel locomotive runs there is found in the general body of the air an amount of carbon monoxide exceeding 0.01 per cent. by volume, the manager shall ensure that no engine of a diesel locomotive is run at that place or at any other place at which such running could affect the ventilation at the first mentioned place until it has been determined that the amount of carbon monoxide in the general body of the air at the first mentioned place does not exceed 0.005 per cent. by volume.

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Source: https://www.legislation.gov.uk/uksi/1956/1771/schedule/FIRST/paragraph/30 (the official version)
Page: https://openlegislation.uk/coal-and-other-mines-locomotives-order-1956/schedule-FIRST/paragraph-30
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.