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.