The invention is directed to an apparatus and a method for surveying and analyzing flow signals that can be picked up by means of flow measuring arrangements in the flow through breathing gas supply systems, in particular CPAP devices, air humidifiers, breathing gas lines, and breathing masks. One aspect of the invention is to furnish ways to increase the reliability of flow signals. In one embodiment, there is provided a device for evaluating a flow signal, picked up from a line provided for carrying breathing gas, having an electronic measurement data processor. The measurement data processor is configured such that it subjects the measurement data detected to a time-frequency-amplitude (TFA) series analysis and generates recordings, by which for the flow signal, the amplitude value of the frequencies contained is apparent.
