Gaseous hydrogen sulfide determination by discoloration of lead-stabilized PVC

The discoloration of lead-stabilized PVC resulting from its interaction with H2S gas has been investigated as a potential H2S measurement technique. Color measurements of PVC samples exposed to controlled concentrations of H2S over a range of humidities and temperatures demonstrate that toxic H2S concentrations can be detected in less than five minutes. The technique is thus appropriate for industrial applications such as the pretesting of manhole atmospheres prior to entry. Exposure times of several hours are sufficient to detect the much lower H2S concentrations that may be present ambient air; for example, 15 hour exposures are needed for 10 +/- 3 ppb H2S, a level typical of certain oil field, swamp, and sewage treatment areas. The technique is inexpensive and can be performed by unskilled personnel.