Bag filter of coarse efficiency is mainly used for filtration of particle≥5μm in air condition system in order to protect medium filter and prolong its service life.Bag filter of medium efficiency is mainly used for filtration of particles≥1μm in air conditioning system in order to protect sub-HEPA or HEPA filter and prolong its service life. The bag is provided with separators inside to increase filtration area effectively. LENGE imported German ultrosonic bag filter production line which can record hundreds of welding process and weld five layers of bags at the same time. The welding technology can decrease damage of filtration materials, increase welding strength and avoid leakages.