Some Info debunking the idea that masks can be recycled or reused----j
Source:
水煮、喷酒精、照紫外线…… 防病毒口罩不能用这些方法循环使用 - 冠状,都是,再利用,防病毒,很难 - 科技日报 - 汉丰网
Boiled, sprayed with alcohol, irradiated with ultraviolet light ... Anti-virus masks cannot be recycled in these ways
2020-02-03 02:40:28 Source: Science and Technology Daily
Xinhua News Agency reporter Wang Quanchao
With the continued development of the epidemic, anti-virus masks such as N95 (KN95) and medical surgery are still on the market, and the inventory of masks in many families is about to bottom out. So, the Internet began to spread the "remedy" for reusing used masks in the pot, steaming them, boiling them in water, baking them under the ultraviolet lamp, spraying them with alcohol and then drying them.
At first glance, these methods are completely consistent with the weakness of the new type of coronavirus that is afraid of high temperature, alcohol, and ultraviolet rays, and it can indeed kill the virus on the mask. But can anti-virus masks labeled with "disposable" really be on the "infinite cycle" of use, disinfection and reuse?
The reporter from Science and Technology Daily interviewed Prof. Jin Xiangyu, the deputy director of the Industrial Textile Engineering Center of the Ministry of Education and the Department of Nonwoven Materials and Engineering of Donghua University. He has presided over the completion of the "Development of Anti-SARS Virus Protective Textiles" project for the SARS epidemic.
According to the "New Coronavirus Infected Pneumonia Diagnosis and Treatment Scheme (Trial Version 4)", "56 ° C for 30 minutes" can effectively inactivate the virus. Can masks be reused by "steaming and boiling"?
Jin Xiangyu: No. Whether it is N95 or medical surgical masks, their means of achieving "anti-virus" rely on the "filter layer" to adsorb and block micro particles (aerosols) such as viruses, and the filter layer is mainly composed of polypropylene melt-blown ultrafine fibers.
According to design requirements, masks must achieve comfortable barrier ventilation while achieving good barrier effects. Generally, the suction resistance to medical masks cannot exceed 343.2 Pascals (Pa), and the suction resistance of daily protective masks is less than 135 Pascals ( Pa).
Therefore, the mask filter material often needs to undergo "electret treatment" to make it carry a small amount of charge, so that it can still effectively adsorb various particles in the air under relatively fluffy conditions.
There is no doubt that whether it is "steaming" or "boiled", the entry of water will quickly eliminate the charge in the filter layer, resulting in a significant reduction in the filtering effect. At the same time, polypropylene meltblown materials have very thin fibers, which are ten times thinner than hair, with an average of only two microns. They are not resistant to high temperatures. When the temperature is higher than 80 ° C, they will shrink and deform, resulting in structural damage and reduced protective effects.
According to the "New Coronavirus Infected Pneumonia Diagnosis and Treatment Scheme (Trial Version 4)", 75% ethanol can effectively inactivate the virus. Can the used masks be disinfected with alcohol and then dried and reused?
Jin Xiangyu: No. On the one hand, the outer surfaces of medical surgical masks and medical N95 masks have undergone a "water-repellent treatment". Alcohol, water, blood, saliva, etc. are difficult to penetrate. The purpose is to strengthen the protection of doctors and prevent liquid spray from coming into contact with patients. Cause cross infection.
Therefore, it is difficult for the surface to be smeared and sprayed with alcohol to disinfect the inside of the medical mask. On the other hand, alcohol can also damage the waterproof structure of the outer layer of the mask. The reason is that the surface tension of alcohol is very different from that of water. The mask material treated with alcohol will enhance the absorption of water (blood, saliva), which will speed up the mask. Filter layer failed.
According to the "New Coronary Virus Infected Pneumonia Diagnosis and Treatment Scheme (Trial Version 4)", the virus is sensitive to ultraviolet rays. Can UV masks and disinfection cabinets be used to disinfect masks for reuse?
Jin Xiangyu: No. Polypropylene meltblown material is a thermoplastic polymer material, which has poor aging resistance and is very sensitive to ultraviolet rays. After being irradiated with ultraviolet rays, the structure will be destroyed or oxidatively degraded, which will greatly reduce the filtration performance.
The research team has conducted experiments. If N95-level masks are steamed, washed, and sterilized by UV lamps, its filtration efficiency will be rapidly reduced from 95% to less than 60%, which is similar to ordinary gauze masks and cotton masks.
So is there any way to achieve disinfection and reuse of masks?
Jin Xiangyu: For ordinary people, no. The disinfection method adopted in the mask production process is ethylene oxide gas disinfection, which cannot be achieved by ordinary households. Moreover, the mask continuously absorbs the water vapor exhaled by the human body during use, which gradually causes the charge loss of the filter layer and the decrease of the adsorption capacity. It cannot be recovered even after disinfection and drying, and it will not provide a good protective effect. Under the current epidemic conditions, disinfection and reuse of disposable anti-virus masks should not be promoted.
Although medical surgical masks and medical N95 masks are both "disposable", from the designer's point of view, ordinary people do not need to use a protective mask before throwing them away unless they go to hospitals, large supermarkets or contact with suspected patients. It can be used two or three times to reduce the consumption of mask resources.
Further reading
Why medical masks are mostly blue
The outer layer of the medical surgical mask is blue, on the one hand, to relieve the visual fatigue of the doctor at work. The white coat + white mask will be more "dazzling" under the light, which is not conducive to the doctor's long-term work. On the other hand, the blue surface is water-repellent, and different colors are also reminding the user that this face is outward.
What is the difference between medical surgical masks and N95 (KN95)? From the perspective of appearance, ordinary medical surgical masks are flat masks, while N95 masks are often arched design, and fit better to the face. But the filter layers of both are made of polypropylene meltblown material, but the thickness is different. In general, the area density of the filtering layer of general medical surgical masks is about 20 to 30 grams per square meter, while the density of the filtering layer of N95 masks is about 55 to 60 grams per square meter.
