Abstract: A valve unit for controlling the delivery of a combustible gas, in particular for delivery via a gas metering apparatus including a main gas through-flow pipe (2), the unit comprising a servovalve with a first valve seat (3) provided on the pipe and associated with a respective first shutter (6) with diaphragm control (7) for the opening of the seat (3) in opposition to a first return spring (22), an operating chamber (10) for controlling the servovalve, the chamber being in communication with an inlet section (4) of the main pipe (2), upstream of the first valve seat (3), one side (7a) of the diaphragm (7) being subjected to the pressure prevailing in the chamber (10), the other side (7b) being subjected to the pressure prevailing downstream of the first valve seat, in the region of an outlet section (5) of the pipe (2), the operating chamber (10) being in communication with the outlet section (5) via a second valve seat (9) co-operating with a second shutter (8).