Using 100% food grade Polypropylene (PP) as material, the filter cartridge contains no wetting agents, solvents, antistatic agents or binders. By special production technology to control the diameter of PP fiber, the micron rate of filter cartridge is controlled. Removing efficience can reach 98%. The surface layer of the filter cartridge is designed to be low density to assure the high dirt-holding capability, while the inner layer is higher density to keep the accurate filtration ability to small particles. The density type is 30% higher filtration effect than the general type.