Atoms and molecules of gas or liquid can be trapped on a solid surface in a process called adsorption. This is an exothermic process involving a release of heat, and heating the surface increases the probability that an atom will escape within a given time. At a given temperature , the residence time of an adsorbed atom is given by  
where  is the gas constant,  is an activation energy, and  is a prefactor that is correlated with the vibration times of the surface atoms (generally of the order of  seconds).
In vacuum technology, the residence time of gases on the surfaces of a vacuum chamber can determine the pressure due to outgassing. If the chamber can be heated, the above equation shows that the gases can be "baked out"; but if not, then surfaces with a low residence time are needed to achieve ultra-high vacuums.