Abstract: An installation for filling cylinders with gas whose nature is in accordance with a predetermined specification, it comprises a plurality of sources of supply (18, 20), a network of control valves (12), selectively connecting the outlet of each supply gas source to the cylinders, and a unit (16) for controlling the network of valves adapted to control the condition of the valves. The control unit (16) comprises a unit (60) for inputting into a program constituted by a sequence of procedures, each procedure being an elemental task that can be performed by the valves under the control of the control unit (16). It moreover comprises a unit (62) for processing the successive procedures constituting the program. They are adapted to control the network of valves (12) by the sequential performance of the elemental tasks described successively in the sequence of operations.