Vapour permeability is the measure of how strongly a material can resist the barrier passage of any gas (such as water vapour, Oxygen, CO₂ or a hydrocarbon).  Vapour permeability dramatically affects the physical characteristics of most products and materials, from outdoor clothing to missiles and from pizza to industrial seals.

Different gases have varying permeability for the same material.
Generally speaking nitrogen oxide has the lowest vapour permeability and that the vapour permeability of oxygen is 25 times greater.  The vapour permeability for carbon dioxide is 10 to 25 times greater than for nitrogen oxide.

For equipment to measure permeability click here

For information on permeability testing click here

For background information on permeability click here