Understand the Benefit and Harm of UV
What is UV light?
Ultraviolet light, as it says, refers to light beyond violet. According to the wavelength, ultraviolet light is divided into many different kinds, but in our lives, you and I usually contact these three: UV-A, UV-B, and UV-C.
The different UV light brings different benefits
For most people, the first use of UV light is often the time to verify the authenticity of banknotes.
This is the most widespread application of UV-A: it excites fluorescent substances to emit visible light. With the development of technology, ultraviolet light is widely used in industry and our life. For example, UV light glue needs to be cured under UV-A irradiation. These UV light glues are energy-saving, environmentally friendly, and economical, which makes them gradually increase their market share. UV-B is also widely used as a means of treating certain skin diseases. UV-C has been used for a long time in the field of disinfection due to its ability to directly destroy the DNA structure. With the deepening of research, some UV light will also promote the growth of some plants, and because of this, in some plant factories, UV light is also introduced.
As this figure shows, different UV light gives us different benefits and more applications may be found in the future. However, because the atmosphere has absorbed most of the natural UV light, the UV light brought by these artificial light sources also poses some risks.
The different UV light brings different harms
It is important to note that UV-C light does not exist in sunlight due to absorption by the atmosphere, and UV-B is only a small fraction of sunlight because of the absorption by the air. We can think that the ultraviolet part of sunlight is mainly composed of UV-A. Therefore, when exposed to different ultraviolet light, they do different damage to us. Of course, exposure to any kind of high-power UV light source will cause irreversible damage to the eyes. Therefore, the following table is only the damage caused by UV in daily conditions.
Through this table, we know that the damage caused by UV-C light is far more serious than the other two. According to IEC 62471, UV-C without risk must be less than 0.001W/m2, but the value of UV-A and UV-B is less than 10 W/m2. Fortunately, the attenuation of UV-C in the air is very serious, so we have a way to avoid this damage and only enjoy the benefits that UV-C gives us.
How to avoid the harm of UV light?
Usually, the atmosphere helps us block most of the UV light. However, with the more and more frequent use of UV light sources in daily life, especially in recent years, UV-C has been widely used for sterilization and disinfection. How to avoid the damage caused by UV light has become a problem that has to be considered.
Control the time under UV light
According to IEC 62471, without careful lighting design, people should avoid UV-C activities completely, and avoid staying under UV-A and UV-B light sources for more than 100s. If you want to save the cost of lighting design, it is best to install a sensor for the light source to detect whether there is someone in the environment. Once there are people in the room, the UV light source will automatically power off to ensure that people are not harmed by UV light.
Through the lighting design, avoid direct exposure to UV
Due to the recent pandemic, the use of UV-C to disinfect spaces has become a new trend. The disinfection of the space and the activities of people need to be carried out at the same time. At this time, we can prevent people from being exposed to excessive UV-C through lighting design.
Just like the design in the picture, UV-C light is limited to the upper layer of the space and only has a disinfection effect on the air in the upper layer. But with the flow of air, the disinfection of the air in the entire space is slowly completed. People do not need to worry about the harm of UV-C to people, because the intensity of UV-C in the air will decay rapidly, and the UV-C that finally reaches the human body will not cause harm to people.