Coronavirus is spread from person to person, usually when someone comes into contact with the secretion of an infected person. The infectivity of the virus directly affects the route of transmission. Exposure to body fluids from an infected person's coughing or sneezing, or shaking hands with an infected person may cause infection. If your hand touches something that an infected person has touched, and then touches your own mouth, nose, or eyes, the virus may also be transmitted.

Normally, there are about 1 liter of liquid in the lungs of the person. Every time you sneeze, the lungs will spray these liquids like a squeezed water bottle. After reaching the body, they will be divided into more than 40,000 small drops, and each drop contains a large number of viruses and bacteria. Due to the huge thrust in the body, the speed of these liquids can be as high as 35 meters per second, and the propagation distance can reach 3 to 8 meters. So be sure to wear a surgical mask! Even if you come into contact with an infected person, wearing a mask can stop you from inhaling the virus directly in the droplets. Always wash your hands frequently! Even if the virus is left on the hand, washing your hands can stop the virus from entering the body through the hand.

How long can KN95 masks be used?

At present, there is no clear conclusion on the optimal wearing time of KN95 masks abroad, including WHO, and China has not yet made relevant regulations on the use time of masks. Some researchers have conducted relevant research on the protection efficiency and wearing time of KN95 medical protective masks. The results show that the filtration efficiency of KN95 masks is still above 95% for 2 days, and the respiratory resistance does not change much; the filtration efficiency is reduced to 94.7 after wearing KN95 mask for three days. The recommendation given by the US CDC is that if there is no adequate supply of masks, as long as the device is not significantly soiled or damaged (such as creases or tears), it can be considered for reuse.

When the following conditions occur, the mask should be replaced in time:

1. When the respiratory impedance increases significantly;

2. When the mask is damaged or damaged;

3. When the mask and face cannot fit tightly;

4. The mask is contaminated (such as blood stains or droplets).

5. Used in individual wards or patient contact (because the mask has been contaminated);