Choosing an anti haze mask requires knowledge to assess its protective effect. We can evaluate it from five aspects: head and face fit, respiratory resistance, particulate matter filtration efficiency, crowd adaptability, and hygiene safety. At present, ordinary masks and disposable non-woven fabric masks sold in the market may have a certain blocking effect on dust and large particles, but their protection against haze, PM2.5, or microbial particles such as bacteria and viruses is insufficient. To further understand the effectiveness of wearing anti particle masks, scholars from the Chinese Center for Disease Control and Prevention conducted a simple small experiment. The results show that ordinary disposable non-woven masks have a certain ability to filter out particles, but due to the inability to tightly fit the face when worn, they cannot effectively prevent particles when actually worn. Wearing an anti particle mask can reduce PM2.5 concentration, reduce population exposure to particulate matter, and be beneficial for health protection. In combination with the technical requirements of standards such as "Respiratory Protection Self suction Filter Particle respirator" (GB 2626-2019), "Selection, Use and Maintenance of Respiratory Protective Equipment" (GBT 18664-2002), and "Technical Requirements for Medical Protective Masks" (GB 19083-2010), it is recommended to choose masks marked with KN95 or N95 (minimum filtration efficiency of 95% for non oily particles) and FPP2 (minimum filtration efficiency of 94%). In addition, when choosing a mask, factors such as the user's facial shape and comfort should also be considered. Wearing a mask also requires washing hands before and after wearing the mask. The colored side of the mask is facing outward, and the side with the metal plate is facing upwards. Press the metal pieces on the mask tightly along both sides of the nose bridge, so that the mask fits tightly against the face. After wearing a mask, avoid touching it. If it is necessary to touch the mask, wash hands thoroughly before and after touching. After wearing a mask each time, an airtightness check is required: hold the mask with both hands and exhale. If you feel gas leaking from the nose clip, you should readjust the nose clip; If you feel gas leaking from both sides of the mask, you need to further adjust the position of the headband and earband. If it cannot fit tightly to the face, it is necessary to change the mask model. Special groups wearing masks should be cautious. Wearing masks generally increases breathing resistance and stuffiness, and not everyone is suitable for wearing masks. Special populations must be cautious when choosing protective masks. Pregnant women should pay attention to choosing products with good comfort based on their own conditions when wearing protective masks, such as those equipped with exhalation valves to reduce exhalation resistance and stuffiness. Before wearing, they should consult a professional physician to confirm that their physical condition is suitable. Elderly people and patients with chronic diseases have different physical conditions. For example, wearing it may cause discomfort for patients with heart and lung diseases. These people should consult a doctor and seek their professional guidance. Children are in the stage of growth and development, and their facial shape is small. It is generally difficult to achieve a tight fitting effect with adult masks. It is recommended to choose protective masks produced by legitimate manufacturers that are suitable for children to wear. Author: Wang Qiong, Institute of Environmental and Health Related Product Safety, China Center for Disease Control and Prevention. Reviewed by Wu Yaxi: Expert from the National Health Science Popularization Expert Database, China Center for Disease Control and Prevention