Barrer

The barrer is a non-SI unit of permeability of gases used in the membrane technology and contact lens industry.

It is named after the New Zealand-born chemist Richard Barrer.

The barrer is defined as follows: Confusingly, the centimetre notation is used in four different ways.

That is, it measures the rate of fluid flow passing through an area of material with a thickness driven by a given pressure.

Permeance can be expressed as the ratio of the permeability with the thickness of membrane.