The main working principle of the nitrogen adsorption generator is based on physical adsorption. The physisorption process takes place inside a cylinder filled with porous granules. Granules represent a carbon molecular sieve (CMS – carbon molecular sieve) and they are used for adsorption. The granules are about 1.5 mm in size, similar to activated carbon, but with much rarer and smaller pores (size 3 Ȧ). Air under pressure enters the cylinder and passes through a space filled with granules, due to the difference in size between oxygen molecules (2.9 Ȧ) and nitrogen (3.1 Ȧ), nitrogen molecules pass trough the granules while oxygen molecules remain trapped inside the them. The adsorption process in the generator takes place in two columns so that nitrogen of constant concentration comes out at the outlet of the generator.