An apparatus for providing a liquid polymer component having a predefined air content, in particular for producing a plastic foam, comprising a pressure vessel , to which the liquid polymer component can be fed through an opening , a pipeline , in particular tubular screw conveyor, which is arranged on the bottom of the pressure vessel and has a multiplicity of air outlet nozzles , to which air from a compressed-air source arranged outside the pressure vessel can be fed at a predefined pressure in order to exit the air outlet nozzles into the interior space of the pressure vessel , a motor-operated stirring device , which mixes the liquid polymer component with the air exiting the air outlet nozzles , a circulation line having an inflow arranged in the region of the bottom of the pressure vessel and an outflow arranged above the inflow , a pump , which is arranged between the inflow and the outflow and conveys the air-charged polymer component through the circulation line from the inflow to the outflow , and an outlet valve , which is arranged between the pump and the outflow and which makes it possible to feed the air-charged liquid polymer component to a mixing device for mixing with a further polymer component , characterized in that an oxygen sensor is arranged in the circulation line and measures an actual value for the oxygen saturation of the air-charged polymer component , and in that an electronic control device is provided, which is configured to modify the pressure and/or the amount of compressed air fed to the air outlet nozzles on the basis of the actual value for the oxygen saturation measured by the oxygen sensor , in such a way that the oxygen saturation of the liquid polymer component circulating in the circulation line assumes a predefined setpoint value. a pressure vessel , to which the liquid polymer component can be fed through an opening , a pipeline , in particular tubular screw conveyor, which is arranged on the bottom of the pressure vessel and has a multiplicity of air outlet nozzles , to which air from a compressed-air source arranged outside the pressure vessel can be fed at a predefined pressure in order to exit the air outlet nozzles into the interior space of the pressure vessel , a motor-operated stirring device , which mixes the liquid polymer component with the air exiting the air outlet nozzles , a circulation line having an inflow arranged in the region of the bottom of the pressure vessel and an outflow arranged above the inflow , a pump , which is arranged between the inflow and the outflow and conveys the air-charged polymer component through the circulation line from the inflow to the outflow , and an outlet valve , which is arranged between the pump and the outflow and which makes it possible to feed the air-charged liquid polymer component to a mixing device for mixing with a further polymer component , characterized in that an oxygen sensor is arranged in the circulation line and measures an actual value for the oxygen saturation of the air-charged polymer component , and in that an electronic control device is provided, which is configured to modify the pressure and/or the amount of compressed air fed to the air outlet nozzles on the basis of the actual value for the oxygen saturation measured by the oxygen sensor , in such a way that the oxygen saturation of the liquid polymer component circulating in the circulation line assumes a predefined setpoint value. <EOS>