Section 137(12) in The Coal Mines Regulations, 2017
(12)In order to detect spontaneous heating in early stages, the air in the return airway of every depillaring district and, of every goaf which has not been isolated, shall be -(a)tested for percentage of carbon monoxide once at least in every seven days with an automatic detector of a type approved by the Chief Inspector; and(b)completely analysed once at least in every thirty days with a view to determining the ratio CO-formed/ O2- absorbed:Provided that if successive tests show any steady increase in the CO-formed/2 absorbed ratio, suitable measures shall be taken to determine the site of the heating and to deal with it.
