Apparatus for investigating the surface of fibre composite plastic components, comprising: a radiation source , which is configured to convert at least one non-volatile substance at least partially into gas by irradiating a sample surface of a fibre composite plastic component ; a detector unit , which is configured to qualitatively and/or quantitatively detect the at least one substance converted into gas, wherein the apparatus also comprises a measuring bell , which is configured to form around the fibre composite plastic component or adjacent to the fibre composite plastic component a measuring volume , which adjoins the sample surface , wherein the measuring bell comprises a seal of a flexible material, which seals the measuring volume at a transition between the measuring bell and the sample surface , wherein the radiation source is configured to irradiate the sample surface through an energy-permeable coupling-in window in the measuring bell , the measuring bell comprises such a coupling-in window , wherein the apparatus comprises a process monitoring unit , which is configured to detect a temperature prevailing at the sample surface , and wherein the radiation source comprises a controller, which is configured to compare the detected temperature with a predetermined threshold value, which implies a risk of thermal degradation of the sample surface , and to end or reduce the intensity of the irradiation if the temperature exceeds the threshold value, comprises, and wherein the radiation source comprises at least one laser and/or at least one plasma emitter, characterized in that the radiation source is configured to initiate a removal of material of the fibre composite plastic component from the sample surface . a radiation source , which is configured to convert at least one non-volatile substance at least partially into gas by irradiating a sample surface of a fibre composite plastic component ; a detector unit , which is configured to qualitatively and/or quantitatively detect the at least one substance converted into gas, wherein the apparatus also comprises a measuring bell , which is configured to form around the fibre composite plastic component or adjacent to the fibre composite plastic component a measuring volume , which adjoins the sample surface , wherein the measuring bell comprises a seal of a flexible material, which seals the measuring volume at a transition between the measuring bell and the sample surface , wherein the radiation source is configured to irradiate the sample surface through an energy-permeable coupling-in window in the measuring bell , the measuring bell comprises such a coupling-in window , wherein the apparatus comprises a process monitoring unit , which is configured to detect a temperature prevailing at the sample surface , and wherein the radiation source comprises a controller, which is configured to compare the detected temperature with a predetermined threshold value, which implies a risk of thermal degradation of the sample surface , and to end or reduce the intensity of the irradiation if the temperature exceeds the threshold value, comprises, and wherein the radiation source comprises at least one laser and/or at least one plasma emitter, characterized in that the radiation source is configured to initiate a removal of material of the fibre composite plastic component from the sample surface . <EOS>