Measurement of chromia-containing vapors in solid oxide fuel cell systems is useful for monitoring and addressing cell degradation caused by oxidation of the chomia scale formed on alloys for interconnects and balance-of-plant components. One approach to measuring chomium is to use a solid electrolyte with an auxiliary electrode that relates the partial pressure of the chromium-containing species to the mobile species in the electrolyte. One example is YCrO₃ which can equilibrate with the chromium-containing vapor and yttrium in yttria stabilized zirconia to establish an oxygen activity. Another is Na₂CrO₄ which can equilibrate with the chromium-containing vapor to establish a sodium activity. In this paper, results on the use of these systems in chromium sensors will be presented.