776. Special ventilation requirements at coal, etc mines.

At mines of coal, stratified ironstone, shale or fireclay, the manager must take the necessary steps to secure that every airway which, as regards any working face1, is an intake airway and the air in which has not previously ventilated a working face is normally kept free from inflammable gas2; but the requirement does not apply to that part of such an airway which is within 90 metres of the first working place3 at the face4. An airway is not deemed to be kept free from such gas if the average percentage by volume found in six samples taken