Two solid state H2S-sensors using Na-beta-alumina as solid electrolyte and Na2S as auxiliary layer were evaluated in a real coal gasifier. The results obtained in the gasifier revealed that the sensors could survive the aggressive coal gasification atmosphere. The sensors reacted simultaneously and identically on changes of the H2S-pressure. The experimental EMF-values were conform to the theoretical EMF-values and therefore the H2S-concentrations calculated out of the sensor signals agreed with the real ones.