5A molecular sieves are the calcium form of aluminosilicate zeolite A. Their structure forms a network of pores approximately 5 angstroms in diameter, through which small molecules such as water and hydrocarbons up to C3 can pass. This makes them useful for removing water from mixtures with larger molecules. They are also used for separation of oxygen and nitrogen from air by pressure-swing adsorbtion, due to their higher affinity for nitrogen. They can absorb up to 20% of their weight of water, depending on the surrounding water concentration and other conditions. They can be dried for reuse by heating at 200-300C (400-600F).-