An approach to assessing the status of sealed-off fires by examination of fire indices

The advantages and disadvantages of different fire indices in common use, such as CO/O2 deficiency (def.)%, CO2/O2 def.% and CO/CO2 percentage, as well as those proposed in the literature such as the desorbed hydrocarbon index, the CO—residual gas relationship and the C/H ratio of the products of combustion, are discussed in terms of their applicability for determining the extent and intensity of underground sealed fires. Five cases of different types of fires are studied and examined using the above indices. It is inferred that characterisation of fires should be made from fire indices, such as the C/H ratio, CO/O2 def.% and the CO/CO2 percentage, temperature profile studies, pressure differential measurements in stopes and spontaneous heating characteristics of the coal concerned in relation to other mining parameters. Values of C/H ratio above 3 or 4, values of the CO/O2 def.% of > 0.5 and values of CO/CO2 of > 2 are indicative of initiation of active fires. A C/H ratio of ⩾ 20 indicates a blazing fire where wooden props may be burning