1 Introduction
During COVID-19, the masks we can generally be divided into medical protective masks, medical surgical masks, ordinary medical masks, and ordinary non-fat gauze masks. The first three are medical devices, which belong to the management of medical devices. The ordinary gauze one is not managed as medical devices.
2 Three Types of Face Masks
2.1 Medical Protective Masks
Medical protective masks meet the technical requirements for medical protective masks standard. The filtration efficiency of the median aerodynamic diameter (05±2) L/min of (0.24 ± 0.06) m sodium chloride aerosol is not less than 95%. That is, it meets the N95 or FFP2 grades. Under the flow conditions, the suction resistance does not exceed 343.2Pa (35mmH2O).
2.2 Medical Surgical Masks
As for it, the filtration efficiency of the median aerodynamic diameter (0.24 ± 0.06) m sodium chloride aerosol under the air flow rate (30 ± 2) L/min shall not be less than 30%. The bacterial filtration efficiency is not less than 95% for the staphylococcus aureus aerosol with an average particle diameter of (3±0.3) μm under the specified conditions. And the respiratory resistance is at the filtration efficiency flow condition. In addition, its inhalation resistance does not exceed 49Pa and the exhalation resistance does not exceed 29.4Pa.
2.3 Ordinary Medical Masks
They comply with the relevant registered product standards (YZB) or YY/T0969-2013. They generally lack the filtration efficiency requirements for particles and bacteria. Their filtration efficiency requirements for particles and bacteria are lower than medical surgical masks. And medical protective masks are suitable for general protection of medical staff.
3 Protection Efficiency
We see a lot of masks marked with different letters, such as KN95, N90, FFP2, etc., so what do they mean?
According to the minimum filtration efficiency of the filter material, under the specified conditions, the mask body can filter out particulate matter. The larger the value, the higher the protection level and the greater the respiratory resistance.
Masks can be divided into three levels:
1) The lowest filtration efficiency of 95 is actually 95%.
2) The lowest filtration efficiency of 99 is actually 99%.
3) The lowest filtration efficiency of 100 is actually 99.97%.
4 Protection Standards
According to the standard classification, the N marked on the mask represents the US standard, FFP is the European standard, and KN is the Chinese standard.
FFP European standard are making by the European Standards Committee for respiratory protective equipment. The standard is to divide the particulate protection filter material into solid particle protection and liquid particle protection, which are tested and classified by NaCL (sodium chloride) and DOP (paraffin oil) aerosols respectively. The role is to absorb harmful aerosols, including dust, smoke, mist, poisonous gas and poisonous vapor, etc.
Filtering Efficiency
That is, through the filter material, blocking them from being inhaled by people. Qualified solid particle protection filter materials have three levels: P1 (FFP1), P2 (FFP2), and P3 (FFP3) according to the tested particle penetration rate. The minimum filtering effect of FFP1 is ≥80%, the minimum filtering effect of FFP2 is ≥94%, and the minimum filtering effect of FFP3 is ≥97%.
5 Mask Letter Meaning
National Institute of Occupational Safety and Health (NIOSH) makes the American standard for their filter material and filtration efficiency. The U.S NIOSH 42CFR-84 standard is the highest recognized in the world. According to the filter material of the middle layer of the mask, there are three types:
“N” on Masks
N stands for Not resistant to oil, which can protect against non-oily suspended particles. For example, the cooking fume produced by cooking is oily particles, while the droplets produced by people are not oily. Generally, non-oily particulate matter refers to coal dust, cement dust, acid mist, microorganisms, etc. In the current haze pollution, most of the suspended particles are non-oily. Oily particulate matter refers to oil fume, oil mist, asphalt fume, etc.
“R” on Masks
R stands for Resistant to oil, which can protect non-oily and oily suspended particles, but when used for oily particles, the use time should not exceed 8 hours.
P stands for Oil Proof, which can protect against non-oily and oily suspended particles. Compared with the R series, the lasting time of P series is longer. But it depends on the manufacturer’s label.
“KN” on Masks
KN is a Chinese standard, and its detection method is the same as that of the United States. According to the GB2626-2006 standard, masks are divided into KN and KP categories. KN means masks are suitable for filtering non-oily particles, and KP means masks are suitable for filtering oily particles and non-oily particles. The number after the letter represents the protection level of the mask, the larger the number.
6 Protective Difference
What is the difference among the protective effects of these three standard?
How about the protection level among the three different standard masks? Obviously, EU FFP can filter non-oily and oily particles at the same time, while N and KN in the United States and China can only effectively filter non-oily particles. Therefore, the formula for their protective effect is roughly: FFP3>FFP2=N95=KN95>KN90.
7 Mask Selections
So in a special period, how should we choose one correctly?
7.1 Ordinary Medical Masks
1) They can block the splashes exhaled from the oral cavity and nasal cavity. They can be used for one-time hygiene care in ordinary medical environments with the lowest level of protection. It is suitable for general health care activities, such as sanitation, liquid preparation, cleaning bed units, etc., or barrier or protection of particles other than pathogenic microorganisms such as pollen.
7.2 Multi Choices
2)The most effective role of N95 masks is to prevent and control the spread of severe respiratory diseases, such as SARS or influenza, and the covid-19. KN95, N95, FFP2 and above standards masks are suitable for covid-19.
7.3 Studies
3) Studies have shown that within the pre-specified range, surgical masks are no worse than KN95/N95 masks in preventing influenza. It is not necessary to wear N95 masks. General masks can block most of the virus-laden droplets from entering the respiratory tract and prevent the new coronavirus. Wearing a mask is still useful during COVID-19 epidemic. So if you can’t buy an N95 mask, you can also choose a general medical surgical mask.
8 Conclusion
At present, there are many kinds of it on the market. The names of the masks have medical, protective, etc., which may not have the effects described. How do we select correctly? Regardless of whether it is a medical protective mask or a surgical mask, ordinary medical masks are medical devices and have protective functions. Therefore, if conditions permit, try to choose products with a medical device production license and a medical device product registration certificate.
9 Target Population
To sum up, in a relatively high-risk environment, medical protective and surgical masks that can effectively prevent respiratory infections. Medical protective masks are suitable for fever clinics, isolation wards medical staff and confirmed patients to wear when transferring. Medical surgical masks are suitable for wearing suspected cases. The public transportation officers and passengers, taxi drivers, sanitation workers, and service personnel in public places should wear when they are on working.
If you have any interset of it, you can have a further reading from Arduino Project: Inactivated Device for Virus on Mask, and get more useful thhings from Postingtree.
