Permeation is often measured using a gas-chromatograph (photo below).
The material which is to be tested is placed in a test cell (photo below) and the challenging media (gas, liquid or aerosol) is fed into the cell on the outside of the material.
As soon as a molecule of the challenging media has diffused through the material, it will be picked up by a carrier gas (normally nitrogen) and fed into the gas-chromatograph, which detects and "counts" the molecules.
The Breakthrough time is when a stipulated amount of molecules has diffused through the material in a certain amount of time. Different test methods use different breakthrough criterions:
||Used in Product standard
||EN 943, EN 14605
For practical reasons, the normal test duration is 8 hours, which equals a working day at the laboratory, and if there has been no breakthrough at this time, the permeation time is defined as "No breakthrough".