An electrochemical fuel cell system comprising a fuel supply of hydrogen rich gaseous fuel for delivery to a fuel cell. A fuel supply conduit connects the fuel supply and the fuel cell for delivering a fuel stream of the hydrogen rich gaseous fuel to the fuel cell. An impurity sensor is carried by the fuel supply conduit for detecting impurities in the fuel stream prior to the impurities entering the fuel cell. A pressure adjusting mechanism is provided in communication with the impurity sensor being operatively associated with the fuel cell for changing the pressure of the fuel cell. The pressure adjusting mechanism raises the pressure of the fuel cell from a normal operating pressure to an elevated operating pressure when the impurity sensor detects impurities in the fuel stream to prevent the impurities from interfering with fuel cell efficiency.