Outgassing refers to the liberation of gases and vapors from the walls of a vacuum chamber.
Outgassing (mbar · l)
The term outgassing refers to the liberation of gases and vapors from the
walls of a vacuum chamber or other components on the inside of a vacuum
system. This quantity of gas is also characterized by the product of p · V,
where V is the volume of the vessel into which the gases are liberated, and
by p, or better ∆p, the increase in pressure resulting from the introduction
of gases into this volume.