The air permeameter apparatus measures the permeability or conductance of an (undisturbed) soil sample. Air permeability is the property of the soil pore system allowing air to flow through. Generally the pore sizes and their connectivity determine whether a soil has high or low permeability. Air will flow easily through soil with large pores and good connectivity between them. Small pores with the same degree of connectivity would have lower permeability, because air will flow through the soil more slowly. Air permeability is also a function of soil texture and macro-pore volume and connectivity, and a function of the matric potential and water content, because continuous macro-pores which would normally conduct air become increasingly filled with water with an increasing load, depending on the soil and initial water content. Determining the air permeability is required when considering quantified data and interpretation of the pore continuity and its dependency on the matric potential, as well as the effect of mechanical stress application on the anisotropy of pore structure for example.