Abstract: A gas flow monitor is provided, in which a defined range of the closing or nominal flow can be set without engaging functional elements. Furthermore, the original closing or nominal flow can be adjusted or amended, even outside the manufacturing plant. The gas flow monitor consists of a gas-tight housing (1) which comprises an inner valve seat (5) for a closing member (9) which is displaceable within the housing (1) and is guided in a sleeve (6) in a longitudinally displaceable manner by a pin (7) and is held in the open position against the flow direction by the force of a closing spring (11). The housing (1) is connected on the inlet side to a tubular insert (13), the inner contour (14) of which determines the flow profile up to the valve seat (5).