Section 153(2)(a) in The Coal Mines Regulations, 2017
(a)in every ventilating district, not less than six cubic meters per minute of air per person employed in the district on the largest shift or not less than 2.5 cubic meters per minute of air per tonne of daily output, whichever is larger, passes along the last ventilation connection in the district which means the in-bye most gallery in the district along which the air passes;