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.[1] 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 of the same substance.