The Porpos system measures the porosity (ratio of air to overall volume) of felts and foams on the basis of the so-called “air-based” method. Via a process of alternately compressing and decompressing air, the porosity of the sample under analysis can be derived from the resulting pressure changes. Owing to the user-friendliness of the measurement procedure, Porpos is suitable not only for experts as the measurement system guides the user through the entire procedure while the system software controls the measurement cycle and automatically evaluates the results.