Abstract: A gas probe for sampling gas molecules from a fluid. A housing includes an orifice and is adapted to be arranged in gas communication with a test gas sensor. The probe includes a stack of layers, whereby gas sample molecules have to pass through all layers of the stack in order reach the sensor. The stack includes at least a first membrane layer, a first spacer layer, a first filter layer and a second spacer layer. The housing includes an inlet for introducing blocking gas molecules into the second spacer layer and an outlet for discharging blocking gas molecules out of the first spacer layer. The gas probe is connectable to a control unit for controlling the blocking gas flow into the second spacer layer.

Abstract: A system for detection of a leak at a leakage testing point of a test object by a tracer gas. A positionable tracer gas mediating unit has a tip. A marker is attachable at the leakage testing point. A marker detector is associated with the positionable tracer gas mediating unit. The tip of the tracer gas mediating unit is arranged to be positioned within a predetermined distance interval from the marker during a leak detection test. The marker detector is arranged to detect the marker when the tip is positioned within the predetermined distance interval so as to certify a correct positioning of the tip.