Method and apparatus for measuring gas transmission rates of deformable or brittle materials

A method for measuring the gas transmission rate of a sealed manufactured package containing a test gas comprising:

• (a) providing a test chamber including an upper diffusion cell and a lower diffusion cell that when closed form a chamber wall seal, a gas valve inlet and a gas valve outlet in fluid communication with the lower diffusion cell and a mass spectrometer in communication with the upper diffusion cell;
• (b) placing a sealed package containing a test gas in the lower diffusion cell;
• (c) selecting a guard material of a known type and positioning said guard material between the lower diffusion cell and the upper diffusion cell;
• (d) positioning a support grid over the guard material and immediately adjacent the upper diffusion cell;
• (e) closing the upper and lower diffusion cells;
• (f) opening said gas inlet valve and said gas outlet valve;
• (g) providing through said gas inlet valve and out said gas outlet valve a source of a second gas different than the test gas to flush the lower diffusion chamber;
• (h) closing said gas inlet and gas outlet valve;
• (i) operating a mass spectrometer thereby creating a high-vacuum system in the upper diffusion cell;
• and
• (j) measuring the gas transmission rate of the sealed package;
• wherein the guard material has a high gas transmission rate relative to the gas transmission rate of the sealed package and wherein the gas transmission rate of the sealed package is calculated by calculating the reciprocal of the gas transmission rate of the sealed package.