A method of controlling production of a gaseous product produced by one or more production plants such as an air separation plant, having a control system to vary production of the gaseous product. The gaseous product is consumed by a customer in accordance with a varying demand pattern. A storage capacity for the gaseous product which may be the pipeline itself or a gaseous receiver tank is provided. Control is exercised by a fuzzy logic program that utilizes the average rate of change of customer demand and storage capacity pressure to produce control data to vary the production rate of the plant.