ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents. Fluid permeance Permeance is closely related to permeability, but it refers to the extent of penetration of a specific object with given thickness by a liquid or a gas. It is the degee to which a materal or membrane transmits another substance. Units of permeance are volumetric output per unit membrane area per unit trans-membrane pressure. Permeance is also referred to as pressure-normalized flux. Fluid Mechanics Wikipedia