Historically membranes have been used in filter applications because of their small pore diameter, these membranes are known as first generation. Recently, membranes have been developed that are characterized by a dense, non-porous active layer, these are known as second generation membranes and use relative diffusivities to separate components.
Whitefox uses a solution diffusion membrane in a capillary configuration. This configuration has the greatest effective membrane surface area per unit of volume and permits use of high operating pressures. This configuration also solves the operational difficulties inherent in plate and frame membranes. A multitude of individual capillaries are gathered to form fibre bundles which are inserted into housings.