Molecular sieves are desiccants with very specific properties. They are synthetically produced alumina silicates. Zeolites will differentiated because of their crystal lattice structure, since this gave them different sized of pores. Type A zeolites containing sodium in their crystal lattice, characterized the pore diameter is approximately 0.4 nm (pore 4A). The zeolithes with the structure X have a pore size of 0,9nm (9A). The structure of the crystal lattice constant allows a very high internal surface area of up to 1000 m² / g. Along with their high electrostatic adsorptive these molecular sieves are ideal for air drying.
Already at low relative humidity molecular sieves reach a higher capacity. Thus, they are able to dry the supply air very strong. This recommended the use in all cases where the degree of drying is a critical selection criterion. The maximum water uptake is located in a fully saturated environment at about 23% (molecular sieve 4A) and 27% (molecular sieve 13X). A color indicator to show the charge state does not exist.