Section 140(12) in The Coal Mines Regulations, 2011
(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 30 days with a view to determining the ratio CO-formed/O2-absorbed.and the result of every such tests shall be recorded in a bound paged book kept for the purpose duly signed and dated by the person carrying out the test:Provided that if successive tests show any steady increase in the CO-formed/O2 absorbed ratio, suitable measures shall be taken to determine the site of the heating and to deal with it.
