CONTROL OF CARBON MONOXIDE MONITORING SYSTEMS IN MINING.

Recent extensive laboratory tests have shown that the rate of evolution of carbon monoxide is the principal and earliest indication of spontaneous combustion underground. Two techniques for the continuous monitoring of this gas are now in use in British coal mines. In the first system, air from a number of points underground is drawn by pumps through a tube bundle to the surface where it is presented sequentially to surface analyzers, a recorder display indicating the levels of carbon monoxide occurring at each sampling point. Variations in design permit flexibility of the number of points sampled and the frequency of sampling, the types of gases analyzed and the presentation of results obtained. In the second approach, a surface control system routes in turn gas from four points to an underground analyzer, the resulting analog signal being transmitted to the surface by a pulse modulation technique and displayed on a four point recorder. The two techniques are described in detail, with emphasis on the control systems employed, and their relative merits are briefly indicated.