Abstract: A pressure swing apparatus includes two sorption beds, one of which extracts a component from an inlet gas mixture while the other bed is regenerated. Valves are provided for controlling the flow of the inlet gas mixture to each of the sorption beds and for venting the beds during regeneration. Sensors are provided for repetitively sensing ambient pressure and the temperature and pressure of the inlet gas mixture. A microprocessor repeatedly samples the measured temperature and pressures and repetitively calculates adsorption and purging intervals, altering the adsorption and purging intervals by controlling the valve actuations to respond in real time to changes in the conditions of the ambient and the inlet gas and thereby to optimize the production of a product gas from an inlet gas of limited supply and widely varying in temperature and pressure. The invention may be applied in aircraft to produce a breathable gas mixture.