Abstract: An apparatus for the determination of the inner condition of a porous material, particularly a textile material web, and a method for running the apparatus. The apparatus comprises a pressure element and an extracting and collecting element which clamp the material between them; the clamped-in sample is then extracted with a preferably hot extracting fluid. The extract will then be analyzed in order to yield indications of the inner condition of the material and/or of substances present in or on the porous material.