For example, the concept is useful in the flow of liquids through permeable media, especially in hydrology in relation to river and lake bottoms.
In this case, it is an application of intrinsic permeability to a unit of material with a defined area and thickness, and the magnitude of conductance affects the rate of groundwater recharge or interaction with groundwater.
Such systems consist of vacuum chambers and the various flow passages and pumps that connect and maintain them.
Typically, the pressures inside these devices are low enough that the gas inside them is rarefied, meaning here that the mean free path of constituent atoms and molecules is a non-negligible fraction of the dimensions of orifices and passageways.
Under those conditions, the total mass flow through an orifice or conduit is typically linearly proportional to the pressure drop, so that it is convenient to quantify mass flow in terms of the fluid conductance of the constituent components.