Because foam gas diffuser permeability and porosity can change during use, the D892 test method recommends that gas diffuser stones be tested when new, periodically, and preferably after each use. The D6082 method requires verification of the specifications for new gas diffusers and after each set of 10 sample runs or less.
Therefore, the Gas Diffuser Verification Device allows testing for maximum pore diameter and permeability of gas diffuser stones according to the ASTM D892 and D6082 foam test methods. The maximum pore diameter is the diameter in micrometers of a capillary of circular cross-section, which is equivalent to the largest pore of the diffuser under consideration. Permeability is the rate a substance passes through the gas diffuser stone under given conditions.