and fluid catalytic cracking. They are also used in the filtration of air supplies for breathing apparatus, for example those used by scuba divers and firefighters. In such applications, air is supplied by an air compressor and is passed through a cartridge filter which, depending on the application, is filled with molecular sieve and/or activated carbon, finally being used to charge breathing air tanks. Such filtration can remove particulates and compressor exhaust products from the breathing air supply. FDA approval The U.S. FDA has as of April 1, 2012, approved sodium aluminosilicate for direct contact with consumable items under 21 CFR 182.2727. Prior to this approval Europe had used molecular sieves with pharmaceuticals and independent testing suggested that molecular sieves meet all government requirements but the industry had been unwilling to fund the expensive testing required for government approval. Regeneration Methods for regeneration of molecular sieves include pressure change (as in oxygen concentrators), heating and purging with a carrier gas (as when used in ethanol dehydration), or heating under high vacuum. Regeneration temperatures range from to depending on molecular sieve type. In contrast, silica gel can be regenerated by heating it in a regular oven to for two hours. However, some types of silica gel will "pop" when exposed to enough water. This is caused by breakage of the silica spheres when contacting the water. Adsorption capabilities 3Å Approximate chemical formula: ((K2O) (Na2O)) • Al2O3• 2 SiO2 • 9/2 H2O Silica-alumina ratio: SiO2/ Al2O3≈2 Production 3A molecular sieves are produced by cation exchange of potassium for sodium in 4A molecular sieves (See below) Usage 3Å molecular sieves do not adsorb molecules whose diameters are larger than 3 Å. The characteristics of these molecular sieves include fast adsorption speed, frequent regeneration ability, good crushing resistance and pollution resistance. These features can improve both the efficiency and lifetime of the sieve. 3Å molecular sieves are the necessary desiccant in petroleum and chemical industries for refining oil, polymerization, and chemical gas-liquid depth drying. 3Å molecular sieves are used to dry a range of materials, such as ethanol, air, refrigerants, natural gas and unsaturated hydrocarbons. The latter include cracking gas, acetylene, ethylene, propylene and butadiene. 3Å molecular sieve is utilized to remove water from ethanol, which can later be used directly as a bio-fuel or indirectly to produce various products such as chemicals, foods, pharmaceuticals, and more. Since normal distillation cannot remove all the