In the literature, a large number of isotherm models are available which can be categorized
into various groups; kinetic models based on an absorbed monolayer of water (BET model), kinetic models based on a multi-layer and condensed film (GAB model), semi-empirical (Halsey model)
and purely empirical models (e.g. Oswin and Smith models).
The moisture sorption isotherms are unique for every material and must be evaluated experimentally.