1, good facial fit. The air leaked from the mask with a gap is directly inhaled from the gap without passing through the filter material, which seriously reduces the protective effect. Leaks can also cause glasses or goggles to fog. Preferably, the leakage rate is less than 1.5%.
2. The filtration efficiency of the filter material should be high. KN90, KN95 and KN 100, the higher the filtration efficiency, the higher the particle retention rate and the lower the particle penetration rate. Gauze masks, common medical masks and medical surgical masks all have low requirements on particle filtration efficiency. The best is KN95/KN 100/KP 100.
3, the protective effect should be high. The protective effect is the ability of the mask to block particles, which is a comprehensive embodiment of leakage and filtration efficiency. D, C, B, A, preferably Grade A, greater than 90%.
4. The inspiratory resistance should be very low. The higher the inhalation resistance, the more difficult it is to inhale, and the mask will have to be taken off after wearing for a period of time, so it is impossible to continue to protect. Preferably, the inspiratory resistance of KN95 mask is less than 50 Pa.
5, expiratory resistance should be low. The greater the expiratory resistance, the more uncomfortable it is, and it cannot be worn for a long time. The expiratory resistance of KN95 mask is preferably less than 50 Pa.
6. The expiratory valve has good air tightness. If there is an exhalation valve, the time for the air tightness of the exhalation valve to return to normal pressure from-1 180 Pa is preferably more than 50 seconds. The air tightness of the exhalation valve is not enough to effectively isolate external particles, especially toxic gases.
7. The dead space rate should be very low. Dead space rate refers to the proportion of carbon dioxide re-inhaled in the previous exhalation. The lower the ratio, the less carbon dioxide inhaled in the previous exhalation, the fresher the inhaled air and the higher the inhaled oxygen content, preferably less than 0. 1%.
8. The headband, connector and exhalation valve cover are under tension. It will be strong to wear and tightly connected, preferably greater than100 n.
9. Also, the mask has no discoloration, no odor, low formaldehyde content, neutral PH value and no carcinogenic dyes.
10, the mask must have a test report from a third-party professional organization. If the seller does not have a test report or does not show the test data, it is not credible.
The development technology of masks is changing with each passing day, and the protective performance index of traditional masks has fallen behind. You can look at the new mask of Mushengtang, which has more than a dozen patents.