A system for analyzing the pore size of a substrate or device containing substrates adapted to separate fluids and has at least two surfaces, a first and a second surface, which are isolated from, one another and wherein the substrate or devices containing the substrates have an exit for fluids passing through the substrate, comprising: a) a particle generator (15) capable of generating particles of a controlled size; b) a system (18) for creating a pressure differential between the first and the second surface of the substrate; c) a light source (24) spaced front the exit of the substrate or device containing the substrate adapted for illuminating particles exiting the exit of the substrate or device containing the substrate; d) a closed flow path from the particle generator to the first surface of the substrate; e) a substrate or device holder (11) adapted for holding the substrate or device in the proper location in the system; and f) one or more reference images. Also described are methods of utilizing the system to identify pore sizes of substrates.