One or more of physical filter screen, activated carbon and steel wire are compounded. The oil fume removal rate of this kind of products is actually 20~30%, which can not meet the requirements of GB 18483-200 1 when used alone. It is easy to block and needs to be cleaned every week. Photocatalysis, using ultraviolet light to decompose oil mist of oily gas. The oil fume removal rate of this product can reach 90%, which meets the requirements of GB 18483-200 1, provided that a pipeline of at least 30 meters is needed to facilitate the installation of ultraviolet lamps. At present, only imported ultraviolet lamps can guarantee the reliability and durability of products. The disadvantage is that ultraviolet light causes cancer, so it must be sealed tightly and cannot be leaked, which is not good for everyone. By the way, a little leakage can be sterilized. Biological purification, using oil-loving microorganisms to decompose and purify oil mist in lampblack.