Permeability

(1) The capacity of a porous material to conduct or transmit fluids; (2) the time rate of vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch x pound) unit of measurement for permeability is gr/h x ft2(in x Hg/in.), which is commonly referred to as perm/inch units.

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