59Prevention of leakage of air between airways
(1)Where, of any two lengths of different passages in a mine of coal, stratified ironstone, shale or fireclay, one is made after the commencement of this Act '(whatever the date of the making of, or of any part of, the other), then, unless there is (without any steps being taken for the purpose of minimising the leakage of air between them) no, or no appreciable, leakage of air between them, it shall not be lawful to use one as, or as part of, an intake airway and the other as, or as part of, a return airway unless such steps are taken as are necessary for the purpose of minimising the leakage of air between them:
Provided that nothing in the foregoing provisions of this subsection shall render unlawful the use as, or as part of, an airway of so much of any passage in a mine as lies within the relevant distance from a working face to which air is supplied or from which air is drawn off through that airway.
(2)For the purposes of the proviso to the foregoing subsection—
(a)the expression " relevant distance " means, in relation to a working face in a mine, four hundred and fifty feet (measured from any point on that face in a straight line on any plane) or such other distance, so measured (whether greater or less than four hundred and fifty feet), as may, in any particular case, be determined by an inspector by notice served on the manager of the mine; and
(b)the expression " working face " does not include a place in a road at which ripping or work of repair is in progress.