of the pressure profiles and the expected performance of the unit more specifically fig6 extracts a detail from the sequence of opening closing commands given by the controller to the valves corresponding to the end of the production elution step and to the beginning of the balancing step the conventions used in this fig6 are as follows empty box filled box transition valve opening command filled box empty box transition valve closing command thus the proposed modification then consists in anticipating the command to open the valves which must normally be closed at the end of the production elution step however it should be noted that in this case given the significant delay in closing the feed valves of the adsorber a 1 and the purge valve of the adsorber a 2 no pressure peak appears at the intake of the vacuum pump pav and at the delivery of the air for roots compressor r which guarantees operating safety and constancy of the specific energy se it is apparent from table ii that a simple adjustment in the controller at start up of the unit is all that is required to take a heterogeneous distribution in o c times into account thus it may be shown that the performance may be maintained as long as the o c times of the valves remain within the range u03bc u2212 0 5 s u03bc 0 5 s with u03bc denoting the average value of the time in question and u03bc being between 0 5 s and 1 5 s the previous study was also carried out on a system having 3 adsorbers in which the risk of a perturbation in the cycle by singular actuation.