Abstract: A method and device for measuring gas permeability through a porous membrane-like material, particularly through paper where a sample is placed tightly against the edges of an open chamber, a gas connection is created to a source of constant pressure, a predetermined pressure difference is used to create a stable flow of gas through the sample, and at least one volume quantity is measured, which is proportional to the gas permeability of the material. The flow of gas is throttled before being led to the chamber, which rapidly stabilizes the flow.