Section 156(2) in The Coal Mines Regulations, 2011
(2)For the purposes of securing adequate ventilation, the owner, agent and manager shall ensure that -(a)in every ventilating district, not less than six cubic metre per minute of air per person employed in the district on the largest shift or not less than 2.5 cubic metres per minute of air per tonne output daily, whichever is larger, is passed along the last ventilation connection in the district i.e., the inbye-most gallery in the district along which the air passes;(b)at every place in the mine where person are required to work or pass, the air does not contain less than 19 percent of oxygen or more than 0.5 percent of carbondioxide or any noxious gas in quantity likely to affect the health of any person;(c)the percentage of inflammable gas does not exceed 0.75 in the general body of the return air of any ventilating district and 1.25 in any place in the mine;(d)the wet bulb temperature in any working place does not exceed 33.5 degrees centigrade and where the wet bulb temperature exceeds 30.5 degrees centigrade, arrangements are made to ventilate the same with a current of air moving at a speed of not less than one metre per second,and for ensuring compliance with the provisions of clauses (b), (c) and (d) of this sub-regulation; air samples and temperature readings shall be taken at least once in 30 days and the result shall be recorded in a bound paged book kept for the purpose:Provided that where at any mine or part, special conditions exist which make compliance with any of the above provisions not necessary or reasonably not practicable the Chief Inspector may, by an order in writing and subject to such conditions as he may specify therein, grant a relaxation from the provisions.
