An apparatus for providing a liquid polymer component with a predefined air content, in particular for producing a plastic foam, includes a pressure vessel receiving the liquid polymer component through an opening, a pipeline at the bottom of the pressure vessel having a multiplicity of air outlet nozzles, a motor-operated stirring device, a circulation line, a pump between the inflow and outflow, and an outlet valve between the pump and the outflow. An oxygen sensor in the circulation line measures an actual value of the oxygen saturation of the air-charged polymer component, and an electronic control device modifies the pressure and/or amount of the compressed air supplied to the air outlet nozzles based on the actual value of the oxygen saturation measured by the oxygen sensor, such that the oxygen saturation of the liquid polymer component circulated in the circulation line assumes a predefined setpoint value.