A pressure swing adsorption system including a plurality of vessels having one or more layers of adsorbent material therein (1 to 7), a feed gas channel (110), a waste channel (120), and a product channel (130). The system also includes at least one parallel channel (140) connected to each of the vessels via a respective conduit with a valve (14), At least one pressure measuring device (M2) is configured to measure a pressure within the parallel channel. And, a controller is provided that is configured to monitor the at least one pressure measured by the at least one pressure measuring deviceduring a PSA cycle performed within the PSA system, in order to determine the performance of the cycle and monitor proper operation of the system.