Why do we need a face mask 

Coronavirus is transmitted between people, usually when someone is exposed to the secretions of the infected person. The transmission of the virus directly affects the transmission route. The current route of transmission of the new coronavirus is unclear, but past experience has shown that exposure to the body fluid that the infected person coughs or sprays, or shaking hands with the infected person lead to infection. If your hand touches something that the infected person has touched and then touches your own mouth, nose or eyes, it may also infect the virus.

Normally, people have about a litre of fluid in their lungs, which, each time they sneeze, spray like a squeezed water bottle. In vitro, they are divided into more than 40,000 droplets, each containing a large number of viruses and bacteria. Because of the huge thrust in the body, the velocity of these liquids can be as high as 35 m / s, and the propagation distance can reach 3~8 m. Come on, this picture is more intuitive.

So be sure to wear a mask! Even if you are exposed to an infected person, wearing a mask can prevent you from inhaling the virus directly from the droplets.

Wash your hands! Even if the virus is left in hand, hand washing can block the virus through the hand into the body.

What's the difference between KN95 and N95? 

N95 mask actually is a kind of respirator, a kind of respiratory protection equipment, which is designed to fit the face more tightly than the ordinary mask, and can filter the particles in the air very effectively. The character "N" indicates that it can be used to protect non-oil suspended particles; 95 means that the filtration efficiency is greater than or equal to 95%, indicating that after careful testing, this respirator can block at least 95% of very small (0.3 micron level) test particles.

By design, if ranked according to the priority of the wearer`s own protective ability (from high to low): N95 masks > surgical masks > ordinary medical masks, ordinary cotton masks.

If worn correctly, the N95`s filtering ability is better than the ordinary mask and medical mask. However, even if worn in full compliance ,100 per cent of the risk of infection or death can not be eliminated.

KN95 is one of the levels specified in the Chinese Standard GB2626-2006.

N95 is one of the grades specified in 42 CFR 84.

The technical requirements and test methods of these two levels are basically the same.

are the filtration efficiency reached 95% under the corresponding standard.

How long can a KN95 mask be used? 

Nowadays, there is no clear conclusion about the best wearing time of N95 masks abroad, including WHO, and there is no relevant regulation on the use time of masks in China.

Some researchers have studied the protective efficiency and wearing time of N95 medical masks. The results show that the filtration efficiency remains above 95% N95 wearing the masks for 2 days, and the respiratory resistance changes little, and the filtration efficiency decreases to 94.7% for 3 days.

a suggestion from the us CDC is that in the absence of adequate supply of masks, reuse may be considered as long as the equipment is not visibly soiled or damaged (e.g. creased or torn).

Change the mask in time when:

  • When the respiratory impedance increases significantly

  • When the mask is damaged or damaged

  • When the mask and face can not close

  • Contaminated masks (e.g. when contaminated with foreign bodies such as blood stains or droplets)

  • Used in individual ward or patient contact (as the mask has been contaminated)