More and more countries recommend wearing masks and questions about masks are increasing:

"What if I can't get a mask?"

"How to protect myself when the mask is almost used up?"

"Can I use any other masks than N95 if it is not available?"

 "Can the mask be used again after I wore it for a while outside ?"

Let’s discuss these questions according to the "Guidelines for the Selection and Use of Masks for the Prevention of New Coronavirus Infections in Different Populations" (hereinafter referred to as "Guidelines") of National Health Commission of the People’s Republic of China.

In order to save some masks, everyone has tried all kinds of methods: microwave heating, oven baking, steamer steaming, sun exposure, spray alcohol ... so are these methods useful? Let's discuss them one by one.

1.Microwave / oven / steamer heating

Whether it is a microwave, electric oven or steamer to heat the mask is a wrong approach. On the one hand, the internal structure of the mask is destroyed, which is easy to cause the mask to deform and the filtration efficiency reduced, so it cannot be used again, and  on the other hand, microwave ovens, electric ovens and steamers are not recommended to continue to heat food due to the treatment of medical waste.

2.Basking in the sun

The novel coronavirus is sensitive to ultraviolet light and heat, but it will be inactivated only when the temperature is above 56 °C for 30 minutes, or when it is exposed to ultraviolet light. The temperature of the sun irradiated to the mask can not reach 56 ℃, and the current season, under normal circumstances, the sun's ultraviolet intensity is not enough.

3.Heavy alcohol spraying

The outer material of the mask will be denatured, the blocking ability of water (blood, saliva) will be reduced, and the filtering function of the mask will be greatly reduced or even invalid with this method.

4.Disinfection

It is also possible to damage the filter layer of the mask, and there is even a problem of residual disinfectant components. For example, if soaked in 84 disinfectant, if the disinfectant cannot be thoroughly cleaned, it may cause facial skin allergies and allergic rhinitis.

If the mask is contaminated with viruses or bacteria, improper operation during the "disinfection" process will easily cause secondary pollution, so it is not recommended that you disinfect yourself.

If you want to use the mask again, the correct approach should be: hang in a clean, dry and ventilated place, or place it in a clean, breathable paper bag. Masks need to be stored separately to avoid contact with each other, and identify the person who uses the mask.

Pharmacies are out of stock, online stores are out of stock, and purchases are not available ... The masks bought before may not be much left. Of course, the ultimate solution is to go out less or not. However, there are always some times when we have to go out, we can consider the following ways:

1.Low-risk exposed people may not wear masks in certain environments

The "Guide" recommends that people with low risk exposure may not wear masks at home, in well-ventilated places with low personnel density. If you encounter a person, it is recommended to maintain a distance of more than 1 to 2 meters.

Low-risk groups include:

● Indoor activist, scattered residents;

● Outdoor activist, including children and students in open spaces / fields;

● Workers in a well-ventilated workplace.

2.Properly extend the use time and frequency of masks

In principle, the masks are disposable, and generally need to be replaced within 4 hours. However, the expert's suggestion is that in some cases, it is possible to properly extend the use time of the mask.

● Ordinary medical mask

It can be used 2 ~ 3 times in non-crowded places.

If there are few people in contact when you just go downstairs to take delivery, take food or throw garbage, the pollution of the mask is relatively small, then just keep the mask intact and continue to use it next time. If you go to a crowded place, the mask is not dirty, damaged, or deformed, and you are not in close contact with the other person, then the mask can continue to be used.

However, if you go to hospitals and other places with high virus density, or have been in contact with suspected patients, the masks used must be disposed of in time.

● N95 masks

in case of shortage of masks, multiple use can be considered (no more than 5 times is recommended)

There is no official recommendation for the length of time N95 masks should be worn. However, from some existing research, even if you wear N95 mask for 2 days, the average filtration rate is still above 95%, and the protective effect is still good. However, if there is increased respiratory resistance, it should be replaced.

Although the mask can be used again, there are three points to note:

(1) Wash your hands before and after wearing a mask, especially if you wear it twice;

(2) Remove the mask by taking the mask strap by hand. Do not touch the outside of the mask to avoid contamination by the virus and bacteria on the mask surface;

(3)Hang it in a clean, dry and ventilated place, or place it in a clean, breathable paper bag.

3.Non-medical masks (such as cotton yarn, activated carbon and sponge masks) can be selected according to the actual situation

Considering the shortage of masks, the "Guidelines" also explains non-medical masks. For low-risk groups, non-medical masks, such as cotton yarn, activated carbon, and sponge masks, have certain protective effects, and also reduce the spread of droplets generated by coughing, sneezing, and talking. They can be used as appropriate.