Wiktionary
n. The slow release of gas from a solid or liquid; especially the release of gases into the atmosphere of a planet vb. (present participle of outgas English)
WordNet
See outgas
Wikipedia
Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. Outgassing can include sublimation and evaporation which are phase transitions of a substance into a gas, as well as desorption, seepage from cracks or internal volumes and gaseous products of slow chemical reactions. Boiling is generally thought of as a separate phenomenon from outgassing because it consists of a phase transition of a liquid into a vapor made of the same substance.
Usage examples of "outgassing".
Apart from much else, our lively interior created the outgassing that helped to build an atmosphere and provided us with the magnetic field that shields us from cosmic radiation.
Back in the 1950s a test on living in an enclosed environment had ended early because the floor covering, some sort of linoleum, turned out to be outgassing some really toxic stuff and everybody in the experiment got sick.
Huge flows of hot melted rock poured out over the floors of the Pacific and Indian oceans, raising sea levels, while outgassing of carbon dioxide created a greenhouse effect.