Knowledge and application of UVC ultraviolet rays

Scientists have widely used the technology of UVC rays for more than 40 years. UVC rays have an effect on all bacteria and viruses that have been tested.

1. The principle of UVC sterilization

According to the wavelength, ultraviolet light is usually divided into UVA (315nm-400nm), UVB (280nm-315nm), and UVC (200nm-280nm). Among the ultraviolet rays of each wavelength, only short-wave ultraviolet UVC has a sterilization and disinfection effect, which is a pure physical disinfection method.

The UVC rays destroy the molecular structure of microorganisms (bacteria, viruses and other pathogens) in a short period of time. Ultraviolet rays irradiate bacteria, viruses and other microorganisms, destroying the molecular structure of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) in the microbial cells, resulting in DNA strand breaks, cross-linking of nucleic acids and proteins to break, causing growth cell death and regenerative cell death, achieving the effect of sterilization and disinfection. It is widely used in the sterilization and disinfection of water and air. Among them, the UVC wavelength with the best bactericidal effect is 253.7nm.

2. The sterilization advantages of UVC

Compared with other sterilization methods such as chlorination, ozone and ultraviolet mercury lamp sterilization, UVC LED sterilization has more advantages:

High-efficiency sterilization: The inactivation effect of ultraviolet rays on bacteria and viruses is generally completed within a few seconds, which occurs almost instantaneously. The sterilization and disinfection capacity is 600 to 3000 times that of chlorine. With traditional water sterilization methods (chloride and ozone methods), it takes about 20 minutes to 1 hour to reach the sterilization efficiency of UVC lights.

Broad-spectrum sterilization: Among all the current sterilization technologies, broad-spectrum ultraviolet sterilization is the highest. Since bacteria, virus antigens and other microorganisms are not resistant to ultraviolet light, UVC light can kill almost all bacteria and viruses with high efficiency. And the sterilization technology of UVC can inhibit the growth of some higher aquatic organisms, such as algae, bloodworms, and paramecium to a certain extent.

Safe and reliable: The most obvious advantage of UVC lamps over the mercury-activated ultraviolet lamps currently on the market is that their germicidal light source does not contain mercury. Mercury is a heavy metal substance. Mercury can evaporate at room temperature. Mercury vapor and mercury The compound is highly toxic (chronic). In the sterilization process of the traditional mercury lamp germicidal lamp, once the lamp tube is broken, it will cause serious water pollution. The UVC LED lamp is a safe and reliable device that does not contain heavy metals and is simple to operate and run. 

No drug resistance: UVC rays directly destroy DNA, RNA, protein, etc. in bacteria and viruses, causing cells to die directly and unable to replicate and reproduce, and there is no drug resistance. When other chemical agents are sterilized, they will cause bacteria and viruses to develop drug resistance, thereby causing the sterilization of the chemical agents to become ineffective.

Energy saving: long life and low maintenance cost. UVC leds are gradually replacing traditional mercury lamps on the market. One of the important reasons is that LEDs have low power consumption. UVC light bulbs have about one-tenth of the power of mercury lamps, which greatly saves costs.

Small size: flexible design, easy installation, the small size of  UVC LED lamp, flexible design of its sterilization device, can be installed and applied in the narrow space where traditional UVC ultraviolet mercury lamp cannot be used.

3. UVC sterilization efficiency

Depending on the type of microorganisms, the sterilization time and dosage of UVC ultraviolet rays are also different. Different bacterial species have different absorption peaks of ultraviolet light. For example, the maximum absorption wavelength of DNA and E. coli are both 265nm, while the maximum absorption wavelengths of Cryptosporidium and bacteriophages are 261nm and 271nm, respectively. Therefore, the required sterilization time should also be different. When the ultraviolet radiation intensity is 3×104μW/cm², the time required to kill viruses and bacteria, mold spores, and algae bacteria is 0.1～1.0s, 1.0～8.0s, and 5.0～40.0s, respectively. According to the research team of the Institute of Viral Disease Control and Prevention of the Chinese Center for Disease Control and Prevention, UVC with an intensity greater than 90 μW/cm² can kill the SARS virus in 30 minutes.

UV dose plays an important role in the disinfection process. UV dose can be expressed as the product of UV light intensity and exposure time. In the case of sufficient UV dose, the inactivated viruses and bacteria will not be resurrected. When the dose is insufficient, some of the inactivated viruses and bacteria will repair damaged structures with the help of light. When the ultraviolet dose is the same, high-intensity, short-time or low-intensity, long-term irradiation can be used to achieve the purpose of sterilization. 

4. Prevent the damage of UVC ultraviolet rays to the human body

The main part of human body damage caused by UVC ultraviolet rays is the eyes and bare skin. Short-term high-intensity irradiation can burn eyes and skin, and long-term high-intensity irradiation can even cause skin cancer.

The penetration of UVC ray is extremely weak, and ordinary transparent glass, clothes, plastic, dust, etc. can be completely blocked. Therefore, wearing glasses (avoid looking directly at the ultraviolet light if you don't have glasses) and covering your bare skin with your clothes as much as possible can protect your eyes and skin from UVC rays.

Short-term exposure to UV rays is like exposure to the hot sun, which is not harmful to the human body but beneficial. UVC ultraviolet rays can promote the metabolism of minerals and the formation of vitamin D in the body.

In rare cases, people who are directly exposed to UVC light for a long time may experience temporary eye and skin damage, such as corneal damage, although this usually heals within a few days. Therefore, the safety advice is to protect the skin and eyes from UVC radiation.

Principles to prevent UVC damage: 

1) Wear glasses (both ordinary glass or resin lenses); 

2) Avoid looking directly at the ultraviolet light;

3) Wear long-sleeved clothes to cover bare skin such as hands; 

4) Use nearby objects to block Ultraviolet rays, such as walls, furniture, curtains, books, newspapers, etc; 

5) Avoid prolonged exposure to ultraviolet rays, and short-term exposure will not harm the human body.

30LEDs/m UVC LED strips with lens 

15LEDs/pcs UVC LED bar with lens

Waterproof UVC LED Rigid Bar

5. UVC LED application

（1）Water Disinfection

As the demand for safer and more effective disinfection methods continues to grow, UVC LED is an effective method to obtain affordable, microbiologically safe water sources.

Static water irradiation：

According to the formula: radiation dose (mJ/cm²) = radiation time (s) ×UVC radiation intensity (mW/cm²), it can be seen that the efficiency of ultraviolet sterilization is related to the ultraviolet radiation dose received by bacteria. In static water irradiation, there are two ways to improve the sterilization efficiency of UVC LED: 1) increase the irradiation time; 2) increase the intensity of UVC LED irradiation. Under the condition that the power of UVC LED light remains unchanged, extending the irradiation time can increase its sterilization rate. When the sterilization time is constant, the greater the input current of the UVC LED, the greater the optical power, and the greater its radiation energy, and the greater the amount of ultraviolet radiation the bacteria receive, so the higher the sterilization rate. At the same time, for a UVC LED with a certain input current, extending the irradiation time can also increase its total radiation energy. The greater the total radiation received by the bacteria, the higher the sterilization rate.

Dynamic water irradiation：

For dynamic water sterilization, when the UVC LED irradiates the dynamic water, the irradiation time is determined by the water flow rate. In the case of a certain UVC line intensity, the larger the water flow, the shorter the irradiation time, the lower the irradiation dose received by the bacteria, and the worse the sterilization effect. The reason is that the faster the water flow, the less time the bacteria receive UVC radiation, which leads to the low dose of UVC radiation received by the bacteria, so the sterilization efficiency is reduced.

（2）Air purification

As a new generation of the green light source, UVC LED provides an effective solution for air purification with its unique safety and economic advantages. The UVC LED air sterilization and disinfection system can also be used on any equipment that requires fresh and fresh air, such as air purifiers, refrigerators, etc. Refrigerators without UVC LED sterilization modules have a natural bacterial attenuation rate of 30%, while refrigerators with UVC LED sterilization modules have a bacterial decay rate of 85%, which also proves the sterilization effect of UVC LEDs and makes the refrigerator freezer compartment The air bacteria content is maintained at a low level, which greatly improves the fresh-keeping capacity of the refrigerator.

（3）Surface Disinfection

When people sneeze or cough, the droplets they release will fall on the surface of nearby objects, such as desks and computers. Since the virus can survive on plastic and metal surfaces for 4-5 days, the specific survival time depends on the temperature, humidity and virus load of the surface environment. Other people may come into contact with contaminated surfaces and become infected.

In high-contact areas such as restaurants, schools, retail stores, laboratories, and public transportation, UVC LED products can be used for deep disinfection of the surface of objects.The light of UVC inactivates the virus on the surface by destroying nucleic acid and damaging its DNA, making the growing cells die and unable to replicate, achieving the effect of sterilization and disinfection.

UVC lighting can not only kill viruses and bacteria efficiently, but also ensure a higher level of protection without the use of additional chemicals. And it has a very high cost performance. When using UVC LED products, it runs around the clock and does not require additional time for maintenance.

If you have any other questions or further requirements, please click here to email the Suntech team or call +(86) 13184617165 for priority-free consultation.

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