Differential radon measurements for outburst prediction in coal mines

In some areas, coal mines are subject to occasional outbursts consisting mainly of carbon dioxide or methane and coal dust. These vary widely in severity. but can cause loss of life. There are several techniques which may permit prediction of the outbursts. These include monitoring acoustic signals or continuous measurement of methane, carbon dioxide or radon concentrations. While it is not expected that any one will be adequate on its own, each technique is being studied so that a combination of all can be evaluated. This paper presents an experiment in which the concentration of radon in underground air is measured with high precision upon entry to and leaving a workface. This was considered the most practicable way to detect any radon flux anomalies preceding an outburst in a working mine. There are many practical difficulties in mounting an experiment in an active mine because of the dusty, wet conditions and because of the need for rigorous safety requirements in an environment which may contain an explosive mixture of air and methane. Details of the development of suitable equipment are given, and an analysis made of the first two months of operation.