Measurement of trace quantities of hydrogen sulphide in industrial atmospheres

Abstract

Although methods have been published for the measurement of traces of H2S in air, no mention is made of their reaction to SO2, which is invariably present in the atmosphere, particularly in industrial areas, in concentrations vastly in excess of that of the H2S. In some cases, the calibration and ultimate limits of detection of the methods are also in doubt. The work described here includes a critical practical appraisal of five alternative methods with respect to interference by SO2, maximum flow rate and limit of detection and their accurate calibration to low levels by both volumetric and gas dilution techniques. Modifications to eliminate interference by SO2 are also described. A description is given of a simple portable field apparatus capable of measuring concentrations of H2S down to 10−4 p.p.m. in a 2 h. sampling period, together with typical levels found when using it.