The absolute permeability of a rock is the permeability of the rock to a nonreacting fluid when it is fully saturated with that fluid. It is calculated using the Darcy’s equation, which indicates a direct relationship between the velocity and the pressure gradient during the flow. Absolute air permeability will be measured using a Hassler type apparatus at a selected of the confining pressure values. The method requires pre-cleaned and dried samples. Klinkenberg permeability may be also calculated, if required.