1. The protection level of mask, give you a formula
The model and executive standard of the mask are printed on the left side of the mask. You can choose according to this: n series is American Standard, kn series is Chinese standard, FFP series is European standard, and the greater the number, the higher the protection level.
It is expressed by a formula: ffp3 > FFP2 = N95 = kn95 > Kn90. Generally, N95 series is enough to resist viruses and influenza, and 90 series can resist more than 90%.
2. Ordinary people do not have to use N95 masks
For medical workers, kn95 mask with the standard of gb19083-2010 should be used. But ordinary people and medical personnel who are not exposed to high-pressure liquid splashing can use ordinary kn95 mask, i.e. Chinese standard gb2626-2006.
As long as you wear it, even a cotton mask will work. Ordinary N95, N90, kn95, Kn90, surgical mask and ordinary medical mask are all OK. It doesn't matter whether there is a breathing valve or not. However, if the wearer is suspected of being infected, a medical mask without a valve must be selected to protect the surrounding people.
3. If the mask is really insufficient, N95 can be reused
Some researchers have studied the protective efficiency and wearing time of N95 medical mask. The results show that the filtering efficiency remains above 95% and the respiratory resistance changes little after wearing N95 mask for 2 days; the filtering efficiency reduces to 94.7% after wearing N95 mask for 3 days.
The CDC's recommendation is that in case of insufficient supply, the N95 mask can be considered for reuse as long as it is not visibly soiled or damaged (such as creases or tears). And the general surgical mask is best thrown away after one use.
4. Correct wearing method and remember the three steps
（1） Wash your hands before wearing the mask to remove the bacteria and viruses that may be on your hands.
（2）When wearing masks, distinguish between inside and outside, and then adjust the metal piece on the nose bridge tightly with the nose bridge. The mandible should also be smoothed and adhered to ensure that it does not leak from around.
（3） "Dirty things" are on the outside of the mask, so when wearing or removing the mask, you should avoid touching the outside of the mask with your hands, and wash your hands thoroughly after removing.
5. Two ways to check the sealing of the mask
（1） After wearing the mask, put your hands on both sides, up and down of the mask, especially on the chin and above the bridge of nose. If you can feel the gas when exhaling, adjust the position. You can also use feathers or a single layer of toilet paper to see if they float.
（2） Second, cover the mask with both hands. If the mask does not have an air valve, exhale quickly, and the mask with good sealing will bulge. If it is a mask with an air valve, you can breathe in quickly, and the mask with good sealing will collapse inward.
6. Properly discard after removal
Correct handling of used masks is also an important step to block the virus. Generally speaking, the novel coronavirus can not be used as a health care mask for human beings.
But the virus has a latent period. The safest way to deal with this problem is to use 75% medical alcohol to disinfect masks thoroughly, put the mask in the sealed bag, and put it in the medical waste or in the special trash can.
7. In addition to wearing masks, pay attention to the air at home
When the air at home is good, the respiratory tract will become the first line of defense for our immune system. Appropriate humidity is also conducive to reducing the spread of the virus.
It is recommended that you keep the windows open and ventilate every day. The room temperature should be kept at 18-25 ℃, and the humidity should be controlled at 30% - 60%. If there are old people and children, the humidity should be controlled at 45% - 50%. If there are people with respiratory diseases in the home, the humidity should be controlled at 40% - 50%.