The "New Crown" epidemic broke out. UVC ultraviolet sterilization and disinfection lamps were sold out everywhere. In addition to the use by professional hospitals, they were also purchased by enterprises and families for anti-virus products such as masks, drinking fountains, air conditioners and daily necessities. There is no doubt that UVC ultraviolet can effectively kill the "new crown", but people still urgently need the knowledge of popular science UVC ultraviolet antivirus, and the dosage and measurement are the key.
What is a new coronavirus
Coronaviruses are a large family of viruses known to cause colds and severe diseases such as Middle East respiratory syndrome and severe respiratory syndrome. The new coronavirus is a new strain of coronavirus that has never been found in humans before. On January 12, 2020, the World Health Organization officially named the new coronavirus in Wuhan pneumonia epidemic as "2019 new coronavirus (2019-nCoV)". As a newly discovered virus, its spread is strong, so we must pay attention to protection in daily life
Knock on the blackboard, only UVC can disinfect and disinfectI often hear the words "Have more sun, sterilization!" Is this true? Really. But it is not the legendary ultraviolet rays that actually sterilize and disinfect the sun, but the infrared rays that have the heating effect. In other words, the heat caused by the sun kills viruses and bacteria. In summer, it suddenly disappeared because the SARS virus is sensitive to temperature!
So don't expect to kill the virus in the sun this season!So does ultraviolet light have the function of disinfection and sterilization? Yes, but only UVC has this skill. As shown in the figure, ultraviolet light can be divided into UVA, UVB and UVC according to wavelength. Among them, UVA has strong penetration ability. Most of the ultraviolet light received on the ground is UVA, and a small part is UVB with weak penetration ability. The UVC components in sunlight are absorbed in the atmospheric ozone layer and cannot reach the ground. The mid-ultraviolet spectrum area where the solar radiation of 200 ~ 280nm cannot reach the earth is called "sun blind area".
（图片来自于M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91）
The survival rate of SARS virus irradiated by UVA and UVC has a relationship with the irradiation time. UVA has almost no inactivation effect on SARS coronavirus. Under the characteristic ultraviolet wavelength of 254 nm and radiation intensity of 4016 μW / cm², the virus kill rate The value has a linear relationship with the dose (time).
Irradiation of microorganisms such as bacteria and viruses by UVC will destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of the microorganism, causing DNA strand breaks, cross-linking and breaking of nucleic acids and proteins, and causing growing cells Death and regenerative cell death, to achieve the effect of sterilization and disinfection.UVC belongs to a broad-spectrum bactericidal class, which can kill all microorganisms, including bacteria, tuberculosis, viruses, spores, and fungi, but different killing objects require different doses.
Leaving the dose to talk about the effects are all hooligans
Ultraviolet sterilization is not a new technology. It has long been used in the disinfection and sterilization of indoor air, object surfaces, water bodies and other liquids. The effect of ultraviolet disinfection and the target (bacteria or virus type), the environment (water or air, temperature and humidity, flow and volume, etc.), radiation illuminance (also called "radiation intensity" in the medical field), radiation dose, etc. related.
At present, there is no much dose of UVC radiation to effectively kill the new coronavirus, but the research of Professor Dong Xiaoping ’s team in 2003 pointed out that at a distance of 80cm from the germicidal lamp and a radiation intensity greater than 90μW / c㎡, it can effectively kill the virus in 60 minutes. In another study in 2004, placing the UVC light source close to the culture fluid to obtain a radiation intensity of 4016μW / cm2 can kill the virus more efficiently in a few minutes!
Compared with heat sterilization, it takes 45 minutes to kill SARS virus at 75 degrees Celsius, and 90 minutes at 56 and 65 degrees.It can be seen that the effect of UVC killing new coronavirus at a sufficient dose is still very predictable!
Two important physical quantitiesWhen we just talked about the radiation dose, two physical quantities appeared: radiation intensity and radiation dose.
Radiation intensity is the name of the medical community. In the field of measurement, it is called radiance, which refers to the radiant flux per unit area of the illuminated surface. The unit is watts per square meter (W / ㎡), usually written as μW / c ㎡.The ultraviolet radiation dose refers to the ultraviolet energy received per unit area, which is the integral value of ultraviolet radiation illuminance and time, the unit is Joule per square meter (J / ㎡), usually written as mJ / ㎡.
Relative to a source of ultraviolet radiation, the intensity of ultraviolet radiation is not static, and usually decreases gradually with distance, as shown in the following figure.When measuring the radiation irradiance or dose of ultraviolet elimination, the position of the measuring instrument and the ultraviolet radiation source must be clearly defined, and the relationship between the radiation illuminance and time (such as the unstable radiation source) must be recorded.Avoid ultraviolet rays can not be directly disinfected against the skin
Don't think that ultraviolet rays have the function of sterilization and disinfection and directly disinfect yourself. You should know that ultraviolet radiation can also cause irreversible damage to human eyes or skin. The following figure shows the spectral sensitivity curve of ultraviolet damage.
According to the IEC62471 standard, 254nm UVC radiation must be below 0.2μW / c㎡ to ensure long-term exposure safety, and short-term exposure to UVC radiation irradiance cannot exceed 1.7μW / c㎡.
In the IEC 60335 series of safety standards for household and similar electrical appliances, equipment with ultraviolet sterilization system, signs and warnings must be clear, and the corresponding content is given in the description section, so as to avoid danger.
