An electric power generating system is provided that comprises a fuel cell stack
having at least one solid polymer fuel cell, a cooling system having a coolant
flow path that directs coolant to and from the stack, a fuel regulating system
having a fuel flow path and for regulating the supply of fuel from a fuel supply
to the stack via the fuel flow path, and a hydrogen concentration sensor. The sensor
is located in the vicinity of the fuel regulating system and in the coolant flow
path at a location downstream of the stack to detect hydrogen that may have been
discharged by components of the power generating system in the coolant flow path
upstream of the sensor, or by the fuel regulating system. In the event the measured
hydrogen concentration exceeds a threshold level, steps are taken to reduce or
stop the discharge of hydrogen from the power generating system.
