Recently, the epidemic situation of medical masks has been very open, and masks have been out of stock. There are also some bad businessmen who have begun to make a fortune. In the comments of value friends, it is found that we are not very familiar with the standards of medical masks. We have nothing to do when we are free. We should popularize the standards of medical masks. There are not many pictures. Just grab some dry goods. Medical masks are basically divided into three categories: medical protective masks, medical surgical masks and medical general masks. Medical masks are generally available in pharmacies. Most of them are medical masks. The appearance of the mask should be neat and in good shape, and the surface should not be damaged or stained. The structure and size of the mask should cover the wearer's mouth, nose and mandible. It should conform to the design size, and the larger deviation should not exceed ± 5%. Nose clip mask should be equipped with nose clip, which is made of plastic material. The length of nose clip should not be less than 8.0 cm. The mask belt should be easy to wear and take. The breaking strength of each mask belt at the connection point of the mask body shall not be less than 10N. Bacterial filtration efficiency (BFE) the bacterial filtration efficiency of the mask should not be less than 95%. (the same as the bacterial filtration efficiency in YY 0469-2011 medical surgical mask) the gas flow rate of bacterial filtration efficiency test was controlled at 28.3 L / min, and the bacterial aerosol average particle diameter (MPS) was (3.0 ± 0.3) μ M. The ventilation resistance of the two sides of the mask for gas exchange should not be greater than 49pa / cm3. The ventilation resistance test was conducted at the center of the mask. The gas flow rate for the test should be adjusted to (8 ± 0.2) l / min. the diameter of the sample test area was 25 mm, and the test area of the test sample was a. The pressure difference between the two sides of the mask was measured by differential pressure meter or equivalent equipment, and the ventilation resistance was calculated according to the formula Δ P = m / A. Δ p-pressure difference of test sample per square centimeter area, unit: PA / cm ~ 3; M-pressure difference value of test sample, unit: Pa; A-test area of test sample, unit: square centimeter. Microbiological indicators non sterilized masks should meet the following requirements: total bacterial colony count (CFU / g): ≤ 100; coliform bacteria, Pseudomonas aeruginosa, Staphylococcus aureus, hemolytic streptococcus and fungi should not be detected. Sterile masks should be sterile. If the mask is sterilized or disinfected with ethylene oxide, the residual ethylene oxide content shall not exceed 10 μ g / g. Biological evaluation of cytotoxicity: the cytotoxicity of masks should not be greater than grade 2. Skin irritation: the primary irritation score of the mask should not be greater than 0.4. Delayed hypersensitivity: the delayed hypersensitivity of the mask should not be greater than grade 1.