The covid-19 pandemic has raised public awareness of UV disinfection, which is also reflected in the increasing number of LED based products on the market. Ultraviolet light can be used to disinfect air, water and surfaces of various objects. The international ultraviolet Association (iuva) says it can help reduce the risk of transmitting covid-19 virus.Ultraviolet light is divided into several ranges (Figure 1). UV-A or black light ranges from 315 to 400 nm and is used in applications such as light stability testing, curing, phototherapy, insect repellents and tanning beds. Prolonged exposure to UV-A can lead to skin tanning and premature aging.Figure 1 ultraviolet light is divided into several ranges.

UV-B in the wavelength range of 280 ~ 315 nm is dangerous. Because long-term exposure to UV-B is related to the occurrence of skin cancer, skin aging and cataract, commercial applications include maintenance and phototherapy in medicine.The wavelength in the range of 200 ~ 280nm is UV-C. This UV band has nothing to do with skin cancer because photons do not penetrate deeply into the skin, but according to iuva research, exposure to UV-C can cause skin discomfort such as severe burns and damage the retina of the eyes. UV-C photons can also interact with RNA and DNA molecules in microorganisms to effectively destroy them. Mercury vapor lamps that can emit UV-C have been used for disinfection for decades. However, like other forms of lighting, they have transitioned to products using LED light sources.

Health experts believe that the main mode of transmission of covid-19 is through contact with respiratory droplets in the air or on the surface of objects. Currently available LED based sterilization and disinfection products are mainly used for surface disinfection. With the expansion of these equipment markets, more advanced air disinfection systems are most likely to be introduced. The available products have the advantages of being suitable for other types of LED lighting: small size, easy integration with other devices such as presence sensors, and low power consumption requirements. However, these products are often more expensive, and there will be more restrictions on the range of surface areas that can be processed in real time.

The initial focus of the shift to LEDs was the significant reduction in LED life compared to existing mercury vapor lamps. However, this concern is based on the evaluation of continuous operation in traditional applications such as sealed purification systems, and does not take into account that bactericidal products can (and sometimes must) be used intermittently. Like all LEDs, UV-C LEDs can cycle almost indefinitely without adversely affecting the light output; In addition, the mercury vapor lamp needs several minutes of preheating time to reach the maximum light output, and the LED products can almost reach the full output level in an instant. In addition, unlike mercury vapor lamps, led based products can only provide the wavelength required for the best results without wasting energy in the form of invalid wavelengths.

Generally speaking, another problem of sterilization lighting products is the verification of product safety and performance requirements. According to Carl Bloomfield, global director of business infrastructure in Intertek's electrical business, their product evaluation focused on brightness parameters, sterilization statement verification, safety compliance, and applicable EMC. Standards development agencies have begun to test standards, but standards do not yet exist, so Intertek relies on its industry and technical expertise to design evaluation protocols for specific products and their intended applications. Safety compliance can be particularly complex because it depends on the product and its intended use, including fire, electric shock, mechanical risk, optical hazards, UV output and ozone emissions.

In addition to UV disinfection products, there is a relatively new product series called "visible light disinfection (VLD)". These products use indigo (blue purple) wavelengths emitted by LEDs, which is safe for human body to be exposed to for a long time, so as to continuously eliminate bacteria sensitive to these wavelengths.VLD products are usually installed in a space as part of the permanent lighting implementation, and sometimes used in combination with white light sources for general lighting. It is worth noting that VLD disinfection is not effective for all bacteria and is completely ineffective for viruses.