During the current epidemic, "N95" in masks has become an important protective material that the public is rushing to buy, and many automobile companies have also released a variety of "anti-virus cars" or "anti-virus car air-conditioning systems" during this period. He also claimed that putting "N95 masks" on cars can block the new coronavirus, setting off a trend of "hot spots" in the automotive industry.
What exactly is the principle of this kind of technology that can prevent viruses? At present, more and more car brands are promoting the protective marketing of wearing "N95 masks" on their cars during the epidemic. What do you think of these "anti-virus" car products? Can they really meet the protection standards of "N95 masks"? Maybe we still have to start talking about "N95 masks".
What is an N95 mask? What is KN95?
The "N95" masks we are longing for during the epidemic do not actually refer to a specific brand, but refer to the ones that comply with the National Institute for Occupational Safety and Health NIOSH (National? Institute? for? Occupational? Safety? A type of particle protective mask certified by and?Health), that is to say, N95 is actually only one of the nine types of particle protective mask standards certified by NIOSH.
As long as it is a product that meets NIOSH review standards, it can be called an N95 mask. The specific breakdown can be divided into two types: industrial dust protection and medical use. The corresponding Chinese mask standard (GB2626-2006 Respiratory Protective Equipment? Self-priming filtering anti-particulate respirator) is "KN95". The two standards are consistent, so the only difference between N95 and KN95 is the Chinese and American production standard markings. The common American brand 3M? N95 masks on the market are only products produced by 3M Company. There is no need for you to only recognize masks with the 3M trademark.
How does N95/KN95 block viruses? Both droplets and aerosols can be handled
The "N" of N95/KN95 masks means not resistant to oil, while "95" represents non-oily particles with an electrical mobility equivalent diameter ≥0.3?m (microns) . During production testing, the particulate matter sample used by the manufacturer is sodium chloride aerosol with a diameter of 0.1-0.5μm (micron). my country's testing standard is that the filtration effect of KN95 masks on this aerosol can reach ≥95.
Everyone was familiar with N95 before the epidemic. In fact, it came from the need to protect PM2.5 haze at that time. Among the components of haze, PM2.5 adopts an aerodynamic equivalent diameter ≤ 2.5?m ( Micron), so N95/KN95 masks can effectively isolate. In this epidemic, the new coronavirus is generally spread by droplets or contact, and the diameter of droplets is generally greater than 5?m (microns), so it will have a good protective effect.
Even droplet nuclei with a diameter of less than 5 m (microns) formed after rapid evaporation of water form aerosols for transmission. Refer to the national test standards, N95/KN95 masks can also achieve the same The blocking effect is above 95. In daily life, because aerosols diffuse very quickly in the air and the density drops quickly, the actual blocking effect is far higher than the value of 95. Therefore, N95/KN95 masks can effectively block both droplet and aerosol transmission methods of the new coronavirus.
Can the HEPA filter that has been popular recently be called "N95"?
Due to the tense epidemic situation recently, many people have begun to favor the HEPA high-efficiency filter (High Efficiency Particulate Air Filter) technology advocated by some manufacturers, claiming that it can effectively isolate the new coronavirus. In terms of propaganda, the term "biological weapons defense model" is even used.
In fact, the HEPA air conditioning filter standard is set by the DOE US Department of Energy. It is generally made of polypropylene or other composite materials. The test standard generally uses dust particles, which is the same as the medical mask "N95" test. The sodium chloride aerosol used in the standard is different.
The claimed filtration efficiency of ≥0.3?m (micron) particles of the HEPA air conditioning filter reaches 95, but the test for 0.3?m (micron) sodium chloride aerosol will be greatly reduced and cannot reach N95/ Protection requirements for KN95 masks.
In the introduction information of the HEPA air filtration system, we see that the function of this air filtration system is to "effectively prevent pollen, fine particles, bacteria and other pollution sources in the air from entering the car." Bacteria/ The diameter of fungi is generally between 0.5-10μm (microns), which is much larger than viruses. From this point of view, HEPA air filters can only achieve the function of protecting PM2.5. In fact, they are far from the medical N95 standard. The difference cannot be called an "N95 mask truck."
Car anti-haze air conditioning filter element = "N95 mask"? impossible!
Currently, most manufacturers of ordinary automobile cabin filters adopt the QC/T?998-2015 technical standard, which can filter certain air dust, particles, pollutants, etc. However, according to the requirements for graded filtration in this standard, the maximum filtration efficiency of general air conditioning filters for 0.3 μm particles is only ≥75, and the minimum standard is only 25. Therefore, it lacks the blocking ability for microorganisms such as the new coronavirus.
As for the anti-haze air-conditioning filter element, the design standard is to block PM2.5, while also taking into account the performance issues of ventilation volume and dust accumulation. Blindly emphasizing the increase in the density of the air-conditioning filter element will bring about The reduction in ventilation volume will also cause dust deposition, causing the problem of too short service life of the filter element.
In order to achieve the corresponding aerosol blocking ability, the ventilation volume and breathing resistance of N95 masks are relatively large. After being used for a short period of time, they must be replaced in time. For automotive air conditioning filters, to ensure a certain amount of ventilation and durability, the filter resistance needs to be controlled to ensure long-term use of the filter. It is impossible to design products with such virus protection capabilities. As mentioned above, there is nothing you can do to achieve the protection level of N95 masks.
Are today’s anti-virus cars false advertising? Can viruses outside the car be prevented?
The air purification systems currently advertised by many car brands use new filter element materials with smaller pore sizes such as activated carbon, high-efficiency non-woven fabrics, and multi-layer composite media. In addition to purifying dust and harmful gases, they can also The important function is to deal with the intrusion of PM2.5 in haze weather. This type of air conditioning filter element can filter out 95% of dust particles with a size larger than 0.3 μm (microns), so it can easily block the droplets that the new coronavirus is attached to. In this way, driving out can completely block the risk of virus transmission.
However, if a brand claims to wear "N95 masks" on its cars in advertisements, it will still be suspected of false advertising. If you read carefully, the promotional pages of many automobile products will also state in detail that their air-conditioning filtration systems use granular dust during the barrier test, not the sodium chloride aerosol used in the N95 mask test. The filtration effects and barrier effects of the two The levels are completely different. The protective ability of N95 masks can take into account both aerosol and droplet transmission of the new coronavirus, while the filtration system on the car can block general droplet transmission, but the blocking effect on aerosol transmission is not good. Both They cannot be confused.
For the general public, it is impossible to understand such boring and monotonous technical information in such detail. However, the "N95 mask mass production vehicle" and "reaching N95 mask level" in the promotional copy are Very inflammatory. In fact, if you think about how "breath-holding" the N95 mask you have worn these past two days is, you will understand that it is impossible to use this thing in a car air conditioner.
Summary
Before the outbreak, automobile manufacturers had launched various PM2.5/anti-haze air purification systems, including various anti-haze air conditioners including HEPA filters The filter element can easily deal with the droplet transmission of the new coronavirus in this epidemic, so everyone can drive out with confidence. Beware of various car companies promoting "N95 mask mass production cars" or "N95 anti-virus cars". The technical standards of such products are completely different from the N95 mask protection standards, and the "hot spot" approach essentially violates advertising laws. .
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.