Section 162(6) in The Coal Mines Regulations, 2011
(6)Every stopping between the main intake and main return airways shall be constructed of masonry or brickwork or of concrete without reinforcement, not less than 25 centimetres in thickness, and if constructed of properly reinforced concrete, of 15 centimeter thickness or such greater thickness as may be required by the Regional Inspector, and shall be faced with a sufficient thickness of lime or cement plaster to prevent leakage of air.
