All the knowledge about masks during the ravages of covid19

1. Is it really useful to wear a mask?

The answer is beyond doubt: really useful!

Whether from an epidemiological point of view or a clinical research standpoint, there has been a lot of evidence that wearing a mask correctly can effectively prevent the spread of the virus.

A clinical study published in the International Journal of Infectious Diseases in 2008 concluded that masks can effectively prevent the spread of the virus when used correctly.Children with influenza at home are 80% less likely to be diagnosed with the virus if masks are used correctly.

Another study published in the Annals of Internal Medicine reported similar results.The researchers surveyed 400 patients with influenza.They found that family members of these patients had a 70% lower risk of influenza if they washed their hands frequently and wore surgical masks.

But researchers also found that using masks alone, but not washing hands frequently, did not reduce risk.So wearing masks and washing hands frequently should be done at the same time, both of which are indispensable.

2. How to wear masks correctly

It is not just wearing a mask that you can worry about everything and stay away from the virus.Correct wearing methods should be divided into five steps: selection-washing-confirmation-cover-sticker.

(1) Choose a mask with appropriate size for your face;

(2) Wash: Clean hands before wearing masks;

(3) Indeed: determine the completeness of the mask, the positive and negative sides as well as the upper and lower directions, for example, the generally colored side should be outward, and the metal strip along should be upward;

(4) Cover: close the nose, mouth and chin;

_Sticking: metal strips should be pressed by hand along both sides of the nasal bridge to ensure tightness.

3. Types and uses of masks

There are two kinds of masks: masks and respirators. Kn95 and N95 masks, which have been hung by people recently, are common respirators.

Combining recent hot spots and considering the ease of purchase, we list the following common masks (see table below) and compare their use and filtering effect.

Classification of common masks and precautions for use

The filtration effect of various masks is closely related to the size of particles to be filtered.The prevalent coronavirus particles are spherical with a diameter of about 0.125 microns, but the virus is usually transmitted by small particles such as droplets and dust.The droplets naturally produced by humans (e.g., those produced by breathing, talking, sneezing, coughing) contain a variety of physiological electrolytes in cells, mucus and saliva, as well as potential infectious agents (e.g., bacteria, fungi, viruses, etc.).Naturally produced droplets vary in size.Published data suggest that sneezing may produce up to 40,000 droplets with diameters between 0.5 and 12 microns.

4. Differences between general masks, surgical masks and kn95 and N95 masks

(1) Mask

Ordinary masks, also known as masks, are loose disposable devices that create a physical barrier around the wearer’s mouth and nose, separating potential contaminants from the surrounding environment.Different masks have different uses, thicknesses, protective effects and comfort levels.

Common cotton masks and sponge masks are very simple in composition, which are made of different fibers and have limited protective effect. Most surgical masks are self-priming filtering masks. Their working principle is to make the air containing harmful substances filtered through the filter material of the masks and then inhaled or exhaled.

Here we mention surgical masks.Standard surgical masks are divided into three layers: the outer layer is a water barrier to prevent liquid splashing, the middle layer is a filter layer to block 90% of the 5-micron particles, and the inner layer is used to absorb the liquid and moisture released by the wearer.Surgical masks are suitable for basic protection of medical staff or related personnel.

In fact, for the majority of ordinary residents, ordinary masks have been able to provide the antiviral capacity required in most living places, unless you enter and leave densely staffed high-risk public places, in some high-quality Chinese version masks heavy, some disposable non-medical protective masks even provide three layers of antiviral filter layer, for most ordinary people’s antiviral needsTo be fully satisfied.

Composition of common surgical masks

If properly worn, surgical masks can prevent droplets, sprays, or splashes of large particles containing viruses and bacteria from entering the mouth and nose.It also helps to reduce the spills of saliva and respiratory secretions on others, thereby preventing infection.However, surgical masks are not designed to filter or block small (less than 5 microns) particles in the air that may be transmitted by coughing, sneezing, or certain medical procedures.Because surgical masks and face patches are loose and not tight, surgical masks also do not fully protect bacteria, viruses, and other contaminants from entering the wearer’s mouth and nose.

Simply put, ordinary masks have no filters; surgical masks have filters but cannot filter very small (<5 microns) particles.

(2) Kn95 and N95 masks

Kn95 and N95 masks actually belong to respirator, which is a kind of respiratory protection equipment. Compared with ordinary masks, kn95 and N95 masks are designed to fit the face tighter and can filter particulate matter in the air very effectively.The Chinese version of the respirator is named Kkn95, N95. Its antiviral effect is the same as kn95 and N95. N means not resistant to oil and can be used to protect non-oily 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.

If worn correctly, the filtration capacity of kn95 and N95 should be better than that of the ordinary and medical masks mentioned above.However, even if the wear fully meets the requirements, the risk of infection or death cannot be eliminated by 100%.

To function effectively, we need to choose kn95 and N95 masks that are suitable for our face. Before using them, we need to check whether they are suitable. Wear the respirator and adjust the skin band so that the respirator fits tightly to the face without feeling uncomfortable.It is recommended to read the instructions carefully to see what different manufacturers suggest for a “good fit”.

5. Are disposable masks positive and negative?Does wearing back affect the preventive effect?

Surgical masks are divided into three layers, internal and external.Common disposable masks generally have both positive and negative sides. Usually the outer layer prevents splashing of liquid, and the inner layer is water-absorbing and soft, so wearing the reverse will affect the effectiveness.The following methods can be used to check whether the wear is correct:

Touch feeling: soft suction face facing inward, rough waterproof face facing outward;

Metal edge of nose bridge: metal exposed face facing outward, while enclosed face facing inward;

Ear hanging thread: The thread of a general tailor is outside;

Look at color: generally white inward, colored part outward.

6. Does the exhalation valve affect the protective efficacy of kn95 and N95 masks?

Kn95 and N95 are divided into two types: with or without expiratory valve.People with chronic respiratory disease, heart disease or other diseases with dyspnea symptoms may have more difficulty breathing with kn95 and N95 respirators, so using kn95 and N95 masks with exhalation valves can make them easier and help reduce heat accumulation.

The design of the exhalation valve is exquisite.There are several orifice covers.When inhaled, the mouth cap will be closed to ensure that no particles enter.When you exhale, the lid opens to let the damp, hot air out.At the same time, there is a soft lid inside to ensure that no small particles enter.

In these two days, people have a lot of misunderstandings about kn95 and N95 with expiratory valves. Some people believe that there is no protective effect with expiratory valves.A study published in 2008 specifically investigated whether expiratory valves affect protective effects on wearers.The conclusion is that the presence or absence of an exhalation valve does not affect the respiratory protection of the wearer.Simply put, kn95 and N95 with exhalation valves can protect the wearer, but not the people around them.If you are a virus carrier, please choose kn95, N95 without exhalation valve, do not spread the virus.If a sterile environment is to be maintained, kn95 and N95 with expiratory valves should not be used because the wearer may exhale bacteria or viruses.

7. Is kn95, N95, kn95 and N95 disposable?Can it be reused?

In fact, all kn95 and N95 respirators are disposable, and it is impossible to determine the maximum number of safe reuses that a respirator can use under any circumstances.Whether kn95, N95, kkn95, N95 can be safely reused is affected by many factors (e.g. infection risk).But in special cases, unless the product instructions of the masks specifically emphasize “only single use”, reuse can be considered in daily use, but this practice is risky.The most obvious point is that the outside of the respirator has actually been contaminated, but users are not aware that there is a risk of infection when reused.If conditions are limited and reuse is really necessary, several points should be noted:

(1) Confirm that the kn95 and N95 respirators used can not be contaminated.

(2) Hang used kn95 and N95 respirators in designated storage areas or place them in clean and breathable containers, such as paper bags.To minimize potential cross-contamination, store the respirators separately from each other and clearly identify the person using the respirator.Storage containers should be handled or cleaned regularly.

(3) Before and after touching or adjusting the respirator, clean your hands with soap and water or alcohol-containing hand sanitizer.

(4) Avoid touching the inside of the respirator. If you accidentally touch the inside of the respirator, please clean your hands as described above.

_If the respirator is damaged or dirty, or you feel difficult to breathe after wearing it, you should remove it. The method of safely discarding the respirator is similar to the mask: put it in a plastic bag, then put it in a garbage can, and wash your hands after treatment.

8. Is kn95, N95, masks as protective as surgical masks?

Studies have shown that there is no significant difference in the preventive effect of these two masks, which differ several times in price.

Previous studies in laboratory settings have shown that kkn95, N95, kn95, N95 respirators provide better protection against acute respiratory infections than surgical masks.But in the clinical setting, randomized controlled trials of kkn95, N95, kn95, N95 respirators did not show the same benefits.However, it is too early to conclude from the results of a single trial, and the final conclusion remains to be further proved.

A 2012 study found that a face mask that fits tightly to the face provides about 94% protection against airborne viruses, while a kn95, N95 respirator that fits tightly to the face correctly can achieve greater than 99% optimal protection.But loosely wearing any kind of mask can only achieve 60% protection.

Therefore, theoretically, wearing kn95 and N95 correctly will provide more comprehensive protection.But if kn95 and N95 cannot be worn for various reasons, surgical masks are also a good choice.

9. Can PM2.5 masks prevent viral infection?

PM2.5 refers to particles with a diameter of 2.5 microns or smaller, while the term “PM2.5 mask” is not rigorous and should be specifically analyzed for different haze masks.For example, our commonly used foldable valved particulate matter-proof masks of 3M9001 and 3M9002 meet the GB2626-2006 KN90 requirements, which means that in the particulate matter test experiments, it can block at least 90% (0.3 micron level) of the test particles, although the effect is slightly less than kn95, N95, but compared with the general disposable masks, the effect is also good.And more people recommend 3M8210, which itself meets the standards of Kkn95 and N95, so it is possible to prevent viral infection.

Two foldable valved particulate matter respirators (image from network)

In general, if you do not know how to handle the “PM2.5 mask” in your hand, it is recommended to inquire about its product specifications and then judge whether to use it.

10. After using the mask, what should be done?

If the mask is damaged or dirty, or if breathing through it is difficult, a new one should be replaced.If you are in an infectious environment, wrap it up and discard it, or throw it in a hospital garbage bin for infectious waste, and wash or disinfect your hands immediately.Even if there is no infectious distress, to protect yourself and others, it is recommended to put it in a plastic bag and then put it in a trash can.Also, remember to wash and disinfect your hands after handling.

11. Will masks expire?

Most disposable kn95, N95 respirators have a shelf life, which is also related to storage conditions.

Why do masks expire?Because the composition of the mask will degrade over time, affecting its function.Over time, components such as straps and filters of masks may age, affecting the quality of face-matching seals.The type of respirator, filter media, other materials used and date of manufacture vary, and the expiration date varies.

Storage conditions are also key factors affecting shelf life.The following two points should be noted when storing:

(1) Always keep the respirator in its original package;

(2) Where respirators are stored, pollution areas, dust, direct sunlight, extreme temperatures, excessive humidity and harmful chemicals should be avoided.


In terms of design, if the priority is given to the wearer’s own protective capacity (from high to low): kn95, N95 masks > surgical masks > general medical masks > General cotton masks.

Prioritization of protective capacity of different masks to wearers

If you are a virus carrier, please choose kn95, N95 without exhalation valve, do not spread the virus.

Please purchase kn95 and N95 which are manufactured regularly and meet the test standard!Beware of fakes!

Masks are not a panacea, but wearing them properly and washing and disinfecting hands frequently can greatly reduce the chance of being infected.You can choose the most suitable mask according to your environment (the probability of infection with the virus).Although kn95 and N95 have the best protective function, they are not suitable for everyone.Many people will feel uncomfortable wearing kn95 and N95, and can not insist on wearing them. Under such circumstances, it is better to choose surgical masks.Wearing a mask is better than not.

Finally, cut back on going out and not going to crowded places.

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