Abstract: In this method for producing O2 and/or ozone for use in an oxygen consumer and/or an ozone consumer (2, 4), whereby residual oxygen is adsorbed from the consumers and, subsequently, scrubbed in a pressure-swing adsorption system (5); whereby the gas is, at least partially, recirculated to the oxygen consumer or, by preceding it with an ozonizer (3), to the ozone consumer (4); and whereby the amount of oxygen required for the operation of the consumers (2, 4) in addition to the recirculated oxygen is derived from an oxygen source (6, 7) separate from the pressure-swing adsorption system (5) designed for the scrubbing of the recirculated gas.In this connection, the preferred procedure is to feed the gas desorbed from the pressure-swing adsorption system (5) in the process of regeneration, at least partially, into the gas flow adsorbed from the consumers (2, 4) and to recirculate it via the pressure-swing adsorption system (5).