According to the performance characteristics and scope of application, medical masks can be divided into: medical protective masks, medical surgical masks, ordinary medical masks.
1. Medical protective masks
Medical protective mask is suitable for the medical personnel and related personnel of the airborne respiratory infectious disease protection, is a kind of closed self-priming filter type medical protective equipment, high protection grade, especially suitable for clinical activities by airborne or close contact in patients with respiratory tract infection disease transmission by droplets when worn. It can filter the particles in the air and block droplets, blood, body fluids, secretions, etc. It is a disposable product. Medical respirators block most pathogens such as bacteria and viruses. The WHO recommends respirators against particulate matter for medical workers to prevent viral infections in hospital air. 
Medical protective masks meet the technical Requirements for Medical Protective Masks gb19083-2003, and important technical indicators include non-oily particle filtration efficiency and airflow resistance. Specific indicators are as follows: 
1) Filtration efficiency: The filtration efficiency of the aerodynamics median diameter (0.24±0.06) m sodium chloride aerosol was not less than 95% under the condition of air flow rate (85±2) L/min, that is, it conforms to N95 (or FFP2) and above grades. Aerosol - transmitted infectious agents <5 m in diameter or close contact with aerosol - transmitted infectious agents.
2) Suction resistance: The suction resistance shall not exceed 343.2Pa (35mmH2O) under the above flow rate conditions.
3) Spray the sample of the mask under the pressure of 10.9kPa (80mmHg), and no technical indicators such as penetration should appear on the inside of the mask.
4) a nose clip must be fitted on the mask. The nose clip is made of flexible material and the length is >8.5cm.
5) The synthetic blood was sprayed into the mask sample at 10.7kPa (80mmHg) pressure, and no penetration should occur inside the mask.
2. Surgical masks
Surgical masks are suitable for the basic protection of medical personnel or related personnel, as well as the protection of preventing the spread of blood, body fluids and spatters during invasive operation. The protection level is medium, with certain respiratory protection performance. It is mainly worn in the operating room in a clean environment with a cleanliness of less than 100,000, nursing patients with low immune function and performing body cavity puncture. Surgical masks can block most of the bacteria and some of the virus, which can prevent the infection of medical staff, but also prevent the microorganism carried by the medical staff from being discharged directly in the breath, which poses a threat to the patients undergoing surgery. Surgical masks are required to filter bacteria at least 95 percent efficiently. Disposable surgical masks should also be issued to patients with suspicious respiratory tract, so as to prevent the threat of infection to other hospital staff and reduce the risk of cross-infection. However, the efficacy of avoiding infection is not as good as that of medical protective masks. 
In line with yy0469-2004 technical Requirements for Surgical Masks, important technical indicators include filtration efficiency, bacterial filtration efficiency and respiratory resistance. Specific indicators are as follows:
1) Filtration efficiency: The filtration efficiency of the aerodynamic median diameter (0.24±0.06) m sodium chloride aerosol was not less than 30% under the condition of air flow rate (30±2) L/min.
2) Bacterial filtration efficiency: Under the specified conditions, the filtration efficiency of staphylococcus aureus aerosol with the average particle diameter of (3±0.3) m was not less than 95%; Bacterial filtration rate should be ≥95%; The filtration rate of non-oily particles should be ≥30%.
3) Respiratory resistance: Under the filtration efficiency flow condition, the inspiratory resistance shall not exceed 49Pa and the expiratory resistance shall not exceed 29.4Pa. When the pressure difference between the two sides of the mask is △P 49Pa/cm, the gas velocity should be ≥264mm/s.
4) Nose clip and mask belt: The mask should be fitted with a nose clip made of plastic material, and the length of the nose clip should be greater than 8.0cm. The belt of the mask should be easy to wear and take. The breaking strength at the connection point between each belt and the mask body should be greater than 10N.
5) Penetration of synthetic blood: After 2ml of synthetic blood is sprayed onto the outer side of the mask at a pressure of 16.0kPa (120mmHg), no penetration should occur on the inner side of the mask.
6) Flame retardant property: Non-flammable materials shall be used for the mask, which will burn less than 5s after leaving the flame.
7) Residual ethylene oxide: for masks sterilized with ethylene oxide, the residual ethylene oxide should be less than 10 g/g.
8) Skin irritation: The primary irritation index of the mask material should be less than or equal to 0.4, and there should be no allergic reaction.
9) Microbial indicators: Total bacterial colonies ≤20CFU/g, coliform bacteria, pseudomonas aeruginosa, Staphylococcus aureus, streptococcus hemolyticus and fungi are not allowed to be detected. 
3. Ordinary medical masks
The ordinary medical mask is used to block the spatter of oral cavity and nasal cavity. It can be used for one-time health care in ordinary medical environment with the lowest protection level. Suitable for general health care activities, such as sanitary cleaning, liquid dispensing, cleaning sheet yuan, or pathogenic microorganisms other than the particles such as pollen barrier or protection.
Comply with the relevant registration product standards (YZB), the general lack of particles and bacteria filtration efficiency requirements, or filtration efficiency requirements for particles and bacteria under medical surgical masks and medical respirator, for only 0.3 mu m diameter of aerosol reach 20.0% - 25.0% of the protective effect, short of filtration efficiency of particles and bacteria, can not effectively stop the pathogen invasion through respiratory tract, cannot be used for clinical invasive operation, also cannot have protective effect on particles and bacteria, virus, limited to dust particles or aerosols play a mechanical barrier.