The molecular sieve (MS) is one of the materials that exert a significant impact on the performance characteristics of insulating glass units (IGU). The research conducted over the years has shown that the behavior of glazing, reliability, appearance etc. is highly dependent on the quality of the materials used in the process of production. To properly analyze a system like MS is absolutely necessary to take into account factors such as: permanent control of manufacturing processes, reproducibility of all parameters, compliance of raw materials used with the provisions of international standards, processing by qualified and experienced, compliance with the requirements imposed by the market, complete testing in real operating conditions, availability of technical teams in the event of problems, close partnerships with notified laboratories, a good quality-price balance. The parameters need to be analyzed when testing a desiccant is constituted by: the capacity of adsorption of water/moisture content, particle distribution (density and dust), the changes during processing (adsorption / desorption of molecules of gas or air inserted in the interspace insulating glass) , the test Delta T. All these elements are important in determining the period of life of IGU, the amount of material needed to fill the spacer deflection, glass appearance etc. All experts in the field are aware of the importance of molecular sieve adsorption capacity and the effect it exerts on the properties of the finished product. In short, it is vital that this variable to record high levels at a low relative humidity. Also, the calculations show that IGU reliability increases with the parameter in question. To distinguish between the different materials available on the market, testing is recommended to be made at 10% relative humidity (RH) and a temperature of 25 ° C (instead of 32% RH, as provided standard EN 1279-2). It has been demonstrated that in those conditions are recorded different behaviors between different types of MS, and the adsorption capacity of high-performance products are sometimes more than three times higher than the one of the entry level solutions.