For decades, the world has been harnessing ultraviolet (UV) light as a tool. Its power to sterilize has made it essential to the drinking water of billions of people. Research laboratories operate powerful UV lights to clean germs from sensitive equipment. Hospitals and medical facilities use UV light to disinfect and decontaminate surfaces and implements.
But why? What makes UV light so special? What is UV light, even, and how is it different from “normal” light? Most importantly, how does it work to sterilize, clean, and disinfect?
What is UV light?
Ultraviolet light is, literally, beyond the bluest light our eyes can see. Whereas visible light waves have a wavelength anywhere between 380 to 740 nanometers, ultraviolet only reaches as high as 400 nm, and drops as low as 10 nm. That takes essentially all UV light out of visual range.
How does UV light kill germs?
On the spectrum, UV light is subdivided into three smaller bands: UV-A (long-wave), UV-B (middle-wave), and UV-C (short-wave). UV-A has the longest wavelength and is closest to the visible part of the spectrum. UV-C has very short wavelengths and is therefore extremely energetic.
As with sunlight, UV light causes warmth on our skin, but can also damage skin cells to the point that they become tumors, effectively destroying the skin which used to be there. The same kind of process (though a bit milder) causes the irritation and redness of a sunburn.
The science behind all this has been understood for almost 150 years now. Once we understood how and why UV light damages matter (like skin), and once we were able to harness it, we began turning this new weapon on our biological enemies.
Because germs, microbes, and bacteria are all living things composed of DNA, UV light damages them too. Exposure to intense or prolonged UV can, therefore, help destroy these disease-causing bugs and render surfaces free of dangerous organisms.
Can UV Light kill viruses and bacteria?
Yes. UV-C light, under the right conditions, is the only UV light that has been effectively tested to inactivate viruses and kill bacteria, according to several studies including those in a recent Illuminating Engineers Society (IES) report. This type of UV light is also called Germicidal UV.
According to studies, UV-A and UV-B lighting have the ability to kill bacteria but have limited efficacy in the inactivation of viruses. UV-A lighting has been used to effectively sterilize and kill bacteria in healthcare facilities, hotels, and other facilities for many years now.
Hospitals and medical facilities make extensive use of UV lights where the risk of infection is high and costly. Shining down on tables, counters, sinks, faucets, and many other common places, these lights help prevent the spread of costly healthcare-associated infections (HAI) such as staph infections.
Can UV-C lighting effectively inactivate the virus responsible for COVID-19?
Yes, according to the April 2020 IES report. The IES research states, “Yes, if the virus is directly illuminated by UV-C at the effective dose level. UV-C can play an effective role with other methods of disinfection, but it is essential that individuals be protected to prevent UV hazards to the eyes and skin.”
“It is essential that individuals be protected to prevent UV hazards to the eyes and skin.”IES Report, April 2020
One of the problems with this fact is that many people are attempting to create UV-C devices in their homes. Companies have appeared in the last 6 weeks with products that claim to be effective against COVID-19. But these products come from unknown companies and the risk is very high if customers buy UV products that aren’t tested, or do not use them properly.
“From nurses to some guy building a UVC box in their basement, I’m getting calls every day asking for help with setup. It scares me that people are going to hurt themselves with UVC.”Brian Heimbuch, Molecular Biologist, Applied Research Associates
While UV-C light can inactivate viruses like the one responsible for COVID-19, all of the applications that have been tested and sourced by the IES report are meant to treat the air and surfaces. There are no published studies or reports suggesting that UV-C light be used on the human body to disinfect against coronavirus. In fact, UV associations are publicly discouraging the use of UV light on the human body to inactivate viruses or kill bacteria.
What are the most effective UV-C applications to inactivate a virus?
One method of germicidal UV lighting to fight airborne viruses is called upper-room GUV air disinfection. This type of lighting is installed in the air-handling system so that the air circulating through the facility is treated. This method can run for a longer period of time due to the UV-C light not directly reaching personnel in the facility.
There are also lower room fixtures that can eliminate up to 99.9% of bacteria and viruses in a space. While these light fixtures treat the lower areas of a room, they are not meant to be operated while the rooms are occupied, due to the potential UV hazards to occupants. The UV-C lower room fixtures typically decontaminate a space while it is unoccupied.
Hospitals and other facilities solve that problem by only using the disinfecting UV lights when rooms are unoccupied or not busy. Also, some lights are designed to emit brief “flashes” of UV, thereby strobing the surface in front of them.
To prevent skin or eye hazards, UV-C lighting units are built with redundant safety systems so they will not activate while the room is occupied, which will allow them to suspend operations if motion is detected in a room.
Are UV-C disinfection lights effective in medical facilities?
Yes. Hospitals have used UV-C lighting or germicidal UV in several different applications to reduce the spread of infection.
According to the IES report, “Medical treatment facilities are using GUV in three primary ways: 1) upper-room GUV fixtures with air mixing, for controlling airborne pathogens in an occupied space; 2) mobile GUV units, to disinfect high-touch surfaces; and 3) GUV in HVAC air handling units, to treat recirculated air and to reduce mold growth on cooling coils.”
There have also been uses of autonomous (“robot”) systems in some U.S. hospitals in response to COVID-19.
Can downward-facing UV-C lighting be used to inactivate the virus responsible for COVID-19?
Yes. However, in lower room applications where suspended UV-C lighting faces downward, it is critical to ensure the space being treated is unoccupied while the lighting is on.
If there is an environment where viral transmission is highly likely, the IES report states that “it is critical that any persons remaining in the space being disinfected from overhead and side UV-C lamps wear protective clothing and eye protection, or exposure to harmful UV will occur.”
What is Far-UVC Light and Can it Be Used to Decontaminate While People are Present?
Far-UVC is a new technology that has been developed by Columbia University’s Center for Radiological Research, which uses lamps that emit continuous low doses (around 220 nm) of UV-C light that cannot penetrate the skin or eyes.
According to the studies at Columbia, far-UVC is safe for people, but lethal for viruses in the air. This technology is being incorporated into conventional light fixtures by a U.S. lighting company. The idea is that the fixtures would be easy to install in public spaces like airports, cruise ships, train stations, and more.
According to experts that we have spoken to, there are still some barriers and tests to prove the effectiveness and safety of far-UVC. But the studies are promising.
Here is a short Youtube video showing how far-UVC works.
The importance of a trusted advisor to help get the right solution
In times like these, there are so many questions and yet there tends to be much confusion about which solution works to inactivate the virus responsible for COVID-19 and other pathogens.
Everyone is ready to get back to business and the new normal. But we realize there are steps we need to take to get there. FSG has trusted advisors across the U.S. that can help answer your questions about UV-C lighting and other solutions to help you get back to business.
We are product agnostic as well. Finding the right solution for your facility is what we care about. Making sure you get the help you need to keep your employees and customers healthy & safe is what we care about.
Learn more about the UV disinfectant lighting research, whitepapers, and products on our UV Lighting Solutions page.
If your facility has the need for germicidal UV or other disinfectant lighting solutions, call our Guide Center at (512) 615-6615. We are here and we are ready to help.