The aim of the study is to determine the air permeability of porous materials. The sample is placed in the instrument and an air flow is generated through it, which causes a pressure difference over the sample. This pressure difference and the air flow volume are measured, after which they, and the dimensions of the sample, are used to calculate the air permeability of the material. The measurements of a sample which fits into the instrument are 200 mm x 200 mm. The experiment can also be done on loose materials.