Section 146(12)(d) in The Coal Mines Regulations, 2011
(d)no plant for the screening or sorting of coal and as far as practicable, no heap of cinder, cement, sand, mortar or other dry and fine material Shall be placed within 80 metre of the top of any down cast shaft or other intake airway nor shall any such material be so handled as to make it air-borne and drawn into such shaft or airway;