NOVELTY - A hydrogen fueling nozzle (20) comprises housing having a portion that is adapted for coupling to an opening of the container, and sensor(s) (100) that is positioned inside the nozzle. The sensor is for detecting the concentration of hydrogen and emitting a signal indicative of the concentration of hydrogen.    USE - For dispensing hydrogen gas source into a container and for detecting hydrogen gas leaks (claimed).    ADVANTAGE - The invention provides measurement of hydrogen levels when transferring hydrogen from one container to another while utilizing a hydrogen sensor that is selective only to hydrogen, does not cross interfere with other species, does not rely on temperature differentials, does not require a clean and dry environment, and can be positioned inside a nozzle transferring the hydrogen without saturating the sensor.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (a) a method for detecting hydrogen gas leaks during the transfer of hydrogen gas from a hydrogen gas source into a container comprising providing a nozzle coupled at one end to a transfer line (3) from the hydrogen gas source and having an output at its other end, positioning sensor(s) inside the nozzle, coupling the sensor(s) to a controller receiving the signal indicative of the concentration of hydrogen, coupling the output end of the nozzle to an opening of the container, initiating transfer of hydrogen gas from the hydrogen gas source to the container, and alerting an operator or shutting off the transfer of hydrogen gas through the controller when the controller determines that the received signal has reached or exceeds a predetermined hydrogen concentration; and    (b) a hydrogen gas transfer monitoring and control system (22) for dispensing hydrogen gas from a hydrogen gas source into a container and for responding to hydrogen gas leaks comprising nozzle(s) coupled to a hydrogen gas source via a transfer line and control valve (4).    DESCRIPTION OF DRAWING(S) - The figure is a block diagram showing the hydrogen fueling nozzle used with a monitoring and control system for transferring hydrogen between containers.    Transfer line (3)    Control valve (4)    Hydrogen fueling nozzle (20)    Hydrogen gas transfer monitoring and control system (22)    Sensor (100)