UVC deep ultraviolet is not harmful to human skin, but it is more harmful to human eyes. The typical UVC-LED wavelength of 275 nm ultraviolet light is almost 97% absorbed by the stratum corneum of human skin, more than 99.9% absorbed by the stratum corneum and epidermis, and a very small part of the light will hit the dermis. Ultraviolet rays only act on the dermis to cause skin cells to become cancerous. Therefore, it is generally believed that UVC ultraviolet rays have little effect on human skin. Of course, baby skin, including some human skin, is thinner and less resistant to UVC ultraviolet rays. Human eyes are not protected by the stratum corneum. Direct UVC ultraviolet rays will cause lens and corneal lesions. Therefore, it is forbidden to look directly at the lighted UVC-LED lamp beads.

But UVC ultraviolet rays, such as 275 nm, propagate much less deeply in the adult epidermis. After penetrating the stratum corneum, more than 97% of the energy will be absorbed, and finally not even 0.1% of the energy that penetrates into the dermis. Therefore, to be precise, UVC deep ultraviolet is not harmful to human skin, and the human eye without stratum corneum is much more dangerous. Of course, long-term exposure to weak light is also harmful to the human body.

Ultraviolet rays mainly destroy the DNA chain of bacteria and viruses to achieve a disinfection effect

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The reason why ultraviolet rays can effectively kill viruses and bacteria is basically to sterilize by destroying DNA. Because the photon energy of ultraviolet light is very high, it can destroy the DNA chain of bacteria and viruses, and kill bacteria and viruses from the root. "

Different wavelengths of ultraviolet light have different killing effects on bacteria and viruses. The traditional UV mercury lamp may be 253.7 or 254 nanometers, and in fact, the most effective wavelength may not be limited to 254 nanometers. According to the latest research results, the germicidal effect of ultraviolet rays may be higher near 264 nanometers. Based on this principle, it can be said that ultraviolet light has the characteristics of broad-spectrum sterilization. Whether it is bacteria, viruses, algae, spores, and other microorganisms, the killing effect is very significant and the efficiency is very high. Compared with other sterilization methods, one advantage of ultraviolet sterilization is that after the irradiation, the ultraviolet rays are turned off, and there is no chemical process involved or pollution.

If ultraviolet rays are to achieve effective sterilization and disinfection, sufficient energy is required, including sufficient irradiation intensity and sufficient time, and a suitable wavelength band is required. According to the wavelength, from long to short, the ultraviolet band is divided into UVA, UVB, and UVC, of which UVC is the band with the shortest wavelength and the highest energy, and we often call it the deep ultraviolet band. In fact, for sterilization and disinfection, the real and most effective is UVC.

From the perspective of the effective band of sterilization, the wavelength should be between 240nm-280nm, the main ultraviolet wavelength of mercury lamp is 254nm, and the wavelength of ultraviolet LED is generally 275nm. Some studies have pointed out that the 265nm band is the most effective for sterilization. However, from the perspective of practical research, the sterilization effects of 254nm and 275nm are on the same order of magnitude. At present, the new coronavirus is rampant. Research and practice have found that to kill the new coronavirus, the sterilization rate is 99.99%, and the required dose is 1445uJ/cm2

At present, most of the ultraviolet sterilization products sold on the market have made some targeted safety protection designs according to the characteristics of the products. Under normal circumstances, the possibility of harming the human body is relatively low. If there are individual products and the protection design is not in place, it is necessary to avoid looking directly at the UV light source as much as possible.

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