Patent ID: 7685865

Claim:
A method of measuring the rate of permeation of a gas or a vapour including water vapour through a material comprising: providing a test sample made of the material in a gas container between the upstream chamber with volume V up and a downstream chamber with volume V down of the gas container; providing a means to remove gas or vapour from the upstream chamber and the downstream chamber; providing an amount of gas or vapour in the upstream chamber of the gas container; providing one or more sensors in communication with the upstream chamber and downstream chamber for pressure measurement as a function of time; approximating the experimental pressure data with an exponential function with an exponential parameter τ; wherein if it is a gas calculating the rate of permeation dN down /dt from the exponential parameter and the amount of gas N 0 according to ⅆ N down ⅆ t  t = 0 = τ · N 0 · V down V up + V down ⁢ ( 1 + V down V up ) . wherein if it is a vapour calculating the rate of permeation dN down /dt from the exponential parameter and the amount of water vapour N up according to ⅆ N down ⅆ t  t = 0 = τ · N up · V down V up .