General information on gases
Heat treatment atmospheres

The physical properties of gases have been the subject of numerous works [1][2] and, in particular, the Encyclopedia of Gases is a comprehensive example[22].

Gaseous molecules are in constant motion, touching each other only in accidental collisions. The distances between them are generally very large compared to the diameter of the molecules.

Gases therefore do not have their own shape – they have the particularity of occupying all the space available to them – and are compressible [1].