The boiling off of the volatile elements in friction materials Outgassing, while it is continuous over the useful life of the pad, is only noticeable during the bedding in process or when the temperature capability of the pad has been exceeded Under those conditions the volatiles form a layer between the friction materials and the disc surface, smelling bad and causing "green fade"
The release of gas from cooling molten rock or the interior of the Earth Much of the atmosphere's gaseous constituents, like water vapor, nitrogen, and argon, came from outgassing