Disadvantages: compared with other cloth masks, masks can not be cleaned; because the arrangement of fibers has a certain direction, it is easier to tear; compared with other textile masks, the strength and durability of masks are worse than other masks. There are many kinds of use condition editing dust masks, which must be selected according to different operation requirements and working conditions. First of all, it should be selected according to the concentration and toxicity of dust. According to GB / t18664 "selection, use and maintenance of respiratory protective equipment", as half masks, all dust masks are suitable for the environment where the concentration of harmful substances does not exceed 10 times of the occupational exposure limit. Otherwise, full face masks or respirators with higher protection level should be used. If the particulate matter belongs to high toxic substance, carcinogen and radioactive substance, the filtration material with filtration efficiency grade should be selected. If the particles are oily, be sure to select the appropriate filter material. If the particles are needle like fibers, such as slag cotton, asbestos, glass fiber, etc., the mask with micro fiber can not be washed with water, and the mask with micro fiber is easy to cause facial irritation at the sealing part of the face and is not suitable for use. For high temperature and high humidity environment, the mask with exhalation valve will be more comfortable, and the mask that can remove ozone can be used for welding, which can provide additional protection. However, if the ozone concentration is higher than 10 times the occupational health standard, the mask can be replaced, with dust and poison combined filter elements. In the environment where there are no particles but only some peculiar smell, it is much lighter to choose the dust mask with activated carbon layer than to wear the gas mask, such as some laboratory environment, but the technical performance specification of such masks is not specified in the standard.