Chemical sensing in fuel cell systems

Systems and methods of chemical sensing in fuel cell systems (10) are described. In one aspect, a replaceable sacrificial sensor system (20) includes an input (48) that is configured to be coupled to a fuel stream delivery system (14), two or more sacrificial chemical sensor fuel cells (44), and a manifold (46) that is configured to selectively couple the sacrificial chemical sensor fuel cells (44) to the input (48). In another aspect, a fuel cell system (10) includes a main fuel cell, a fuel stream delivery system (14) that is configured to direct a fuel stream to the main fuel cell, an oxidant stream delivery system (16) that is configured to direct an oxidant stream to the main fuel cell, and a sensor system (20). The sensor system (20) is coupled to the fuel stream delivery system (14) at a location upstream of the main fuel cell and includes two or more sacrificial chemical sensors (44) and a manifold (46) that is configured to selectively couple the sacrificial chemical sensors (44) to the fuel stream delivery system (14). A fuel cell monitoring method also is described.