Why do you need to wear mask?

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 liter 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.

In 2003, SARS was so horrifying because the speed at which it was transmitted through droplets was beyond control, with the south-east asian flu on monday, south-south china next monday and the whole country next monday.

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)

Do you need a breathing valve? 

N95 is divided into two types: with exhalation valve / without exhalation valve.

People with chronic respiratory disease, heart disease, or other diseases with dyspnea symptoms may be more difficult to breathe with a N95 respirator, so using a N95 mask with an exhalation valve can make their breath easier and help reduce heat accumulation.

Exhale valve is designed with several layers of mouth cover. When inhaled, the mouth cover will be closed to ensure no particles enter. When exhaled, the mouth cover opens to let the damp and hot air out. At the same time, there is a soft mouth cover inside, which can ensure that no small particles enter.

During these two days, there were many misunderstandings about the N95 with the exhalation valve, and some people thought that the exhalation valve had no protective effect. A study published in 2008 specifically investigated whether exhalation valves affect the protective effects on wearers. Conclusion ——

The absence of an exhalation valve does not affect the breathing protection of the wearer. Briefly, N95 with an exhalation valve can protect the wearer but not the people around. If you are a carrier of the virus, choose a N95, without an exhalation valve and do not spread the virus. If you want to maintain a sterile environment, do not use N95, with an exhalation valve because the wearer may exhale bacteria or viruses.

Correct wearing of KN95 masks 

Earband Wear Method

Headband Wear Method

• Ear band type: easy to wear and pick, suitable for short time out

• Headwear: more tightly fitted and comfortable longer than earband

Choice based on actual needs

Caution of wearing KN95 masks 

• Wash your hands before wearing a mask, or avoid touching the inside side of the mask during wearing a mask to reduce the risk of contamination.

• Clear the inside and outside of the mask, up and down; KN95 the mask has printed side for the outside; metal strip / sponge strip end is the top of the mask.

• Do not use your hands to squeeze the mask, including N95 mask, can only isolate the virus on the surface of the mask, if the hand squeeze the mask, so that the virus with droplets soaked through the mask, there is still a chance to infect the virus.

• Be sure to keep the mask close to your face. The simple test method is: after wearing the mask, exhale hard, the air can not leak out from the edge of the mask.

Mask is not omnipotent, but wear mask correctly, often wash hands to sterilize, can greatly reduce the probability of being infected!

If you are a carrier of coronavirus, choose N95 without the breath valve to prevent spreading virus.

Finally say again, wear masks to wash hands frequently, reduce going out, do not go to crowded places! Hope everyone is safe and healthy.