A gas control system includes: a first valve that is provided in a carrier gas line or in a gas supply line; a flow rate control mechanism that is provided in a diluent gas line and includes a flow rate sensor and a second valve; a contactless type first concentration sensor; a first valve control part; a diluent gas setting flow rate calculation part adapted to, on the basis of a preset setting total flow rate of a post-dilution mixed gas and a post-dilution measured concentration, calculate a diluent gas setting flow rate that is a flow rate of a diluent gas to be flowed through the diluent gas line; and a second valve control part adapted to control the opening level of the second valve so as to decrease the deviation between the diluent gas setting flow rate and a measured flow rate measured by the flow rate sensor.

A method and system for supplying additional hydrogen from a reservoir of stored hydrogen in a salt cavern to a hydrogen pipeline to assist in meeting customer demand for hydrogen is provided. Contaminants introduced while the stored hydrogen stream is in the salt cavern may cause the crude hydrogen stream to not have the required product purity specification. The stored hydrogen is removed from the salt cavern as a crude hydrogen stream and thereafter diluted with higher purity hydrogen formed from the pipeline to form a hydrogen product stream at or below the product purity specification. The hydrogen product can be formed without removal of any of the contaminants in the crude stream, thereby creating a more cost effective and simplified supply process compared to conventional processes employing a salt cavern for hydrogen supply.