The General Administration of market supervision and administration of disposable medical masks and the China Standardization Administration have issued a new respiratory protection standard gb2626-2019, which will be implemented on July 1, 2020. It is reported that the new standard will put forward higher requirements on respiratory resistance, air tightness, practical performance, cleaning and disinfection of kn95 masks, which can better reflect the performance of masks in actual use. In the new standard, the filter element level is divided into kn100, kn95 and Kn90 according to the filtration efficiency level of non oily particles. The filtration efficiency of non oily particles above 0.075 micron can reach 99.97%, 95% and 90%, respectively. The higher the protection level and filtration efficiency, the higher the safety of dust masks. Live delivery with the "behavior guide" should not be false publicity, cheating consumers... 1, ordinary absorbent gauze mask in addition to keeping warm, other aspects do not play any role. Some people think that the better the tightness of the mask, the stronger the ability to block dust and bacteria, and the safer it is for the human body. However, the more airtight the mask is, the more likely it is for people to have obvious dyspnea after wearing it, which will cause adverse harm to human body. 2. Activated carbon mask: the activated carbon mask can effectively block benzene, formaldehyde, odor, odor and other harmful gases in the air to protect human health, but it can not achieve effective blocking effect for fine particles such as "PM2.5". At the same time, activated carbon itself is also a kind of particle, which may be inhaled by the wearer. For patients with chronic respiratory diseases such as COPD or frail people, it is a kind of harm, so patients with COPD should wear it carefully. 3. Medical mask: medical mask is mainly used to filter the exhaled gas to prevent the infection between doctors and patients. Most of them are made of large pore size fibers, which have large pores and can not effectively resist PM2.5. The thicker the mask, the worse the air permeability. If you do not pay attention to the use of hygiene, it will also lead to bacterial reproduction. 4. Fashion masks: Fashion masks are often sold in some jewelry stores with low prices. They contain chemical fiber ingredients. They are printed with colorful cartoon patterns on the front. The sanitary conditions are worrying and the air permeability is poor. Chemical fiber fabrics may stimulate the bronchus, some people will have skin allergy, nose discomfort and other symptoms. Some patients with allergies, asthma, wearing this mask may aggravate the disease. 5. N95 or 3M mask: the fabric and workmanship of N95 or 3M masks are different, but there is no difference in function. The N95 represents this mask

A filtration efficiency is generally measured on particles of 0.3 micron size with a flow rate of 85 L / min,

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