Section 230(1) in The Coal Mines Regulations, 2011
(1)The drill machine shall not be used at a place -(i)where ventilation is such that the velocity of air current is less than 60 meters per minute;(ii)where methane concentration in the general body of the air exceeds 0.5%;(iii)which is in the return airway of the ventilation,unless provided with heavy type of stone dust barriers of a design as specified by the Chief Inspector.
