Paragraph 5

Where in the seam or seams of coal in connection with the working of which any road is used inflammable gas is unknown and no explosive, which is not permitted explosive and sheathed explosive within the meaning assigned to those terms by the Coal Mines (Explosives) Regulations, 1956^f1, is used in that road, the minimum percentage of incombustible matter required shall not exceed sixty per cent. in a case in which the road is treated with incombustible dust or fifty per cent. in a case in which it is not so treated.