UV-C Disinfectant Lights: How do you use UVC Lights?

UV-C Disinfectant Lighting Fixtures

UV-C defines the ultraviolet radiation within the wavelength range of 200-280 nanometers. While the UV-A (400-315 nm) and UV-B (315-280 nm) exposure from the sun or sunbeds have some associated dangers, UV-C, also produced by the sun, is the shortest of the ultraviolet wavelengths and is almost entirely filtered out by the atmosphere before reaching the surface of the earth.

However, while people have little or no natural exposure to it, it has been artificially produced and successfully utilized as a bactericide and germicide for decades. It can kill or inhibit the growth of microorganisms such as viruses, bacteria, fungi, and other pathogens, providing a chemical-free alternative to other disinfection methods like the use of chlorine.

Due to its effectiveness and potency, UV-C lights are being utilized in an increasing range of applications. For instance, it is used for disinfection in laboratories, wastewater treatment plants, pools and aquariums and various stages of food and beverage industrial processes. While traditionally mercury-vapor lamps were used for generating germicidal UV-C, technological advances have made it possible to have UV-C light-emitting diodes (LEDs) leading to a larger number of applications, including the disinfection of medical devices.

One thing worth saying up front, because it is the most common question we get: ordinary white LED lighting does not emit germicidal UV-C. A white LED produces light in the visible band, which is what you want in a commercial lighting or high bay fixture. UV-C LEDs are a separate, purpose-built product class, and anything sold as a general-purpose bulb that claims to disinfect a room should be treated with suspicion. Our UV-C disinfectant lighting guide goes further into how to tell a real germicidal fixture from a fake one.

UV-C Is Great For Killing Germs, Bacteria And Viruses, Including Covid Strains

The UV-C radiation eliminates a wide range of bacteria including the drug-resistant bacteria termed as superbugs, viruses, including many types of flu strains, beta coronaviruses including MERS, SARS and the SARS-CoV-2 virus that causes COVID-19.

According to a study conducted by Hiroshima University researchers, UV-C light fixtures with a wavelength of 222 nanometers, which is safer around humans, effectively eliminates SARS-CoV-2. In their in vitro experiment, the researchers demonstrated that 99.7% of the SARS-CoV-2 viral culture was killed following a 30-second exposure to 222 nanometers UV-C radiation at 0.1 mW/cm2.

Germicidal effectiveness is proportional to the exposure dose (radiant exposure, typically in millijoules per square centimeter) and time. A non-linear relationship exists between UV exposure and germicidal efficacy. That is the number to ask a supplier for, and the one that is most often missing from a spec sheet: not the lamp wattage, but the delivered dose at a stated distance and exposure time.

A wavelength of 222 nm far-UVC is incapable of penetrating the skin and the outer non-living layer of the human eye, and so does not reach the living cells beneath. That property belongs to 222 nm specifically. It does not apply to conventional germicidal UV-C at 254 nm, which does injure eyes and skin on direct exposure and is the reason shielded upper-room systems, interlocks and occupancy controls exist. The FDA has issued safety communications on exactly this point after consumer UV wands were found emitting unsafe levels. Treat the two wavelengths as different products, because they are.

Some of the most stubborn bacteria that the UV-C LED light fixtures have been proven to eliminate include MRSA (Methicillin-Resistant Staphylococcus aureus), Salmonella, ESBL-producing Escherichia coli (E. coli), Clostridium difficile, multi-drug resistant pseudomonas, and Carbapenemase-resistant Klebsiella pneumoniae (KPC).

How Does UV-C Work?

UV-C contains wavelengths in the photobiological ultraviolet spectral band, 200-280 nanometers (nm). This band has been shown to kill bacteria, inactivate viruses and eliminate spores. Hence, it is referred to as germicidal ultraviolet. The UV-C wavelengths comprise photons (particles of light) which are most energetic in the optical spectrum (comprising UV, visible, and infrared) and therefore, are the most photochemically active.

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) is the genetic material that makes up all living things, including microscopic organisms and pathogens such as bacteria, viruses and fungi. It controls their reproduction, growth, development and functioning and without the genetic material, the pathogens cannot reproduce which leads to their death.

The DNA molecules are made up of nucleic acids called adenine (A), cytosine (C), guanine (G), and thymine (T). In RNA, uracil (U) replaces thymine. These acids are held together by chemical bonds which is the target for the UV-C radiation. The electromagnetic energy produced by the UV-C radiation destroys the chemical bonds that hold together the nucleic acid bases.

The photochemical reactions generated in the DNA and RNA by the ultraviolet energy triggers the formation of specific cytosine or thymine dimers in DNA and uracil dimers in RNA. These changes ultimately cause the inactivation of the microbes by inducing mutations that lead to reproduction failure and cell death. Because the mechanism is dose-driven rather than instant, shadowed surfaces and anything out of line of sight do not get treated, which is why fixture placement matters as much as fixture output. The IES committee report CR-2-20 on germicidal ultraviolet is the reference to work from on that.

The LEDs that produce UV radiation have become commonly available and emit a narrow wavelength band with the current fixtures having a peak wavelength at 265 nm, 273 nm and 280 nm among others.

What Types Of UV-C Fixtures Are Available?

Germicidal UV-C lighting is versatile and available in different forms suitable for its many applications. Commonly, UV-C lighting is used in medical settings, in schools, public transportation and for wastewater treatment among others. There is a fixture type suitable for every need. As such, these UV-C fixtures come in different types.

Mobile and portable UV-C disinfection units

Germicidal UV-C light products and systems come in a portable form as mobile UV-C disinfection units. The carts or units can be moved easily from one room to another for the disinfection of multiple spaces. Commonly, they are used in hospitals and other medical facilities following the cleaning of a patient room or operating room, ready for the next patient. These units are placed in the room and activated to disinfect surfaces and air in the space. The units are normally on wheels or tripods and easy to operate and transport. When used with traditional cleaning methods, these units have been shown to reduce bacterial load by 70%.

Wall-mounted

These units are installed on the walls and provide disinfection from the sides. They can be spaced and installed for appropriate disinfection levels based on the size and contours of your facility. This option can disinfect on-demand with preset and controllable cycles. It is even possible to run cycles overnight or any time the spaces are unoccupied. For example, they can be run at night in office space based on the size and the level of disinfection needed.

With motion sensor

These fixtures also come with added features such as motion sensor lighting. When left on to disinfect a space and then the motion sensor installed into the fixture registers movement, the disinfecting UVC LED light turns off to prevent exposing the person who walked in. On a conventional 254 nm system that interlock is not a convenience feature, it is the safety control.

Applications for UV-C Light Fixtures

UVC germicidal fixtures are utilized in a wide range of sterilization applications, providing effective disinfection of surfaces, water and air.

Water UV sterilization - the fixtures are used for the killing of pathogenic microorganisms and bacteria in water with UVC radiation in many environments. They include spas and swimming pools, wastewater treatment, aquaculture, drinking water, ballast water treatment for ships among other water sterilization needs. Their effectiveness has been proven to work against pathogens chlorine has been unable to inactivate, such as giardia and cryptosporidium.

Surface UV sterilization - UVC lamps are used for the disinfection and sterilization of surfaces in many industries and applications including schools, restaurants, hospitals, industrial and commercial properties. In hospitals, UVC radiation is used for the sterilization of surgical equipment, patient and operating rooms, surfaces, patient beds and restrooms. In restaurants, the UVC fixtures sterilize tables people eat on, kitchen exhaust fans, kitchen counter surfaces, walk-in freezers to prevent molds, and refrigerators. In food irradiation, it is used for the preservation of food and the elimination of foodborne microorganisms such as E. coli and salmonella.

Air - UV air purification efficiently disinfects and sterilizes air without the use of hazardous waste or by-products. These fixtures are used in air purification systems such as upper-room UVGI systems, HVAC systems sterilizing furnaces as well as air conditioning units. For the air purification, these fixtures eliminate airborne viruses, preventing the spread of microorganisms such as SARS-CoV-2, responsible for Covid-19.

Related Articles

Footcandles and Lux Guide

Calculate LED Power Load

LED Parking Lot Buyers Guide

About the Author

Dara Greaney

Dara Greaney is founder and CEO of LED Light Expert with deep expertise in commercial LED lighting, retrofits, and photometric planning.

LinkedIn X (Twitter)

Editing by David Peguero