Section 145(1)(d) in The Coal Mines Regulations, 2011
(d)where the parting, with an overlying seam on fire or in which spontaneous heating has taken place, or with surface containing an active fire or spontaneous heating in any spoil heap or ash heap or in any other heap or place, or with any other fire or spontaneous heating which cannot be controlled immediately, consist of less than 10 metres of hard rock, except with the permission in writing of the Chief Inspector and subject to such conditions as he may specify therein.