A comparison of platinum and iridium in work-function measurements with regard to hydrogen sensitivity is presented. The measurements were performed by means of a Kelvin probe and an ISFET-based measurement setup. They are concentrated towards high concentrations of hydrogen and low temperature in order to develop room temperature operated FET-based sensors which can withstand H-2-concentrations of some percent. With both materials the detection of H-2 up to 2% is possible. However, iridium shows very-slow reactions with adsorption as well as with desorption times of some hours. In contrast, the response times of platinum could be determined to be below 10 s in the case of 0.1% H-2. Therefore, platinum is the most promising candidate with air-gap configurations of FET like hybrid suspended gate FET (HSGFET). (C) 2001 Published by Elsevier Science B.V.