Barrer

Barrer is a non-SI unit of gas permeability (specifically, [gas] permeability) used in the membrane technology and contact lens industry. It is named after Richard Barrer.

Definition

1 Barrer = 10⁻¹¹ (Scm³ ) cm cm⁻² s⁻¹ torr⁻¹. Here the 'Scm³ ' is standard cubic centimeter, that is a unit of amount of [gas] rather than a unit of volume. It represents the amount of gas molecules or moles that would take up one cubic centimeter at standard temperature and pressure, as calculated via the ideal gas law.
The cm corresponds in the permeability equations to the thickness of the material whose permeability is being evaluated, and the cm⁻² to the reciprocal of the surface area of that material.