The Science of UV Light against Corona Virus
Using UV Light to kill viruses like COVID-19
For decades, scientists have known about the disinfection ability of ultraviolet wavelengths, specifically germicidal UV (also known as UV-C).
In recent years, germicidal UV helped stop the spread of numerous pathogens like the flu and the superbug. Can germicidal UV also fight the novel coronavirus (or COVID-19)?
The COVID-19 situation is rapidly changing, and it's causing priorities to shift for a lot of us. Protecting patients, customers, workers, and our families is more important than ever before. Disinfecting frequently used surfaces is extremely important, and UV light is very effective at inactivating pathogens like viruses and bacteria.
Germicidal UV products tout pathogen kill rates higher than a 99.9% rate. Because of their effectiveness, they're incredibly useful right now for hospitals, medical labs, senior care centers, fire and police stations, airports, and transit stations but can also be used in schools, government buildings, office buildings, and hotels.
We explain what germicidal UV is, how it works, and the advantages for commercial buildings.
What is UV-C or germicidal UV light?
Germicidal UV or UV-C is part of the ultraviolet spectrum best known for its ability to inactivate pathogens like bacteria and viruses. It utilizes specific wavelengths of the ultraviolet spectrum, typically between 200 to 280 nanometers.
Germicidal UV is typically used to disinfect rooms and surfaces. COVID-19 can live on certain surfaces for up to three days, so it's critical to disinfect at regular intervals.
The Illuminating Engineering Society (IES) recently released a report on germicidal UV, and notes that UV-C is the most effective at disinfection.
Although the science behind germicidal UV has been around for a long time, it hasn't been widely used in the U.S. until recently. The CDC and FEMA started to endorse the use in hospitals in the early 2000s. Since then, several medical reviews have noted the effectiveness and usage has jumped in the last 13 years.
What's the difference between germicidal UV and UV from the sun?
Germicidal UV, or UV-C, is a particular spectrum of ultraviolet light (UV). UV energy occurs naturally from the sunlight or can be generated artificially in light fixtures and bulbs.
Although it is commonly called "UV light," ultraviolet wavelengths fall just outside of the visible light spectrum. Instead of light, UV is scientifically called radiant energy.
For this reason, you won't any see light produced from UV products.
UV wavelengths can range anywhere from 10 nanometers (nm) to 400 nanometers (nm).
Germicidal UV utilizes the wavelengths between 200 to 280 nm. Far-UVC also falls within germicidal UV, but uses a smaller segment of wavelengths. You can read more on far-UVC and its effectiveness below.
UV-A and UV-B light can also kill some bacteria and germs, but is ineffective against viruses like COVID-19.
Read more: Does all UV light kill germs?
Can germicidal UV kill viruses?
Germicidal UV lights can actually change the DNA and RNA of bacteria and viruses, destroying their ability to reproduce.
The IES points out that viruses are not living organisms, so germicidal UV cannot technically "kill" them. Instead, we can say germicidal UV "inactivates" viruses, while it does kill bacteria.
Bacteria may be resistant to other things like antibiotics, but cannot build up a resistance to UV light.
If you're interested in a more scientific definition, check out this explanation from one of our manufacturers.
The big question right now: Can UV lights inactivate COVID-19?
Because this is a novel (or new) coronavirus, testing is very limited but is currently ongoing. The structure of COVID-19 is different from past viruses. For that reason, there is not enough data to say that UV lights can inactivate COVID-19.
Here is what scientists do know. Pathogens can be ranked based on their tolerance to disinfectants, like germicidal UV. Coronaviruses fall into the category of "enveloped viruses," or a Class 3. Class 3 viruses are the easiest to get rid of. Products that are able to inactivate more resilient viruses like small and large non-enveloped viruses (Class 1 & 2 viruses) should also be effective against enveloped viruses like coronaviruses. Many UV product manufacturers say their products can kill most Class 1 viruses.
Based on this information, germicidal UV is believed to be effective against COVID-19.
It's also important to note germicidal UV does not replace other cleaning measures like dusting off surfaces. In fact, germicidal UV products cannot penetrate particles like dust, so dirty surfaces will cause effectiveness to drop.
Is germicidal UV light safe?
Artificial UV light, just like overexposure to the sun, is known to cause side effects for humans like burns so it must be handled following strict safety guidelines.
As a basic rule, germicidal UV lamps should not run when anyone is nearby. The IES says there are no reports of long-term damage from an accidental overexposure, but there can be painful temporary consequences.
Only trained workers should handle germicidal UV units, and make sure the product is turned off before performing maintenance.
What is far-UVC light and is it safe?
Recent studies show certain wavelengths of UV light may be safer than others while still targeting bacteria and viruses.
Far-UVC lamps use a narrow range of UV-C wavelengths, from 207 to 222 nm.
Far-UVC is believed to be just as effective at killing germs as higher ranges of UV-C light, but less harmful to our skin and eyes.
One study in particular focuses on the use of far-UVC light. The study concluded that 222 nm UV can inactivate pathogens but not penetrate the skin. The IES warns that safety may depend on the product's glass envelope, or outer layer of the lamp.
Other studies suggest that wavelengths as low as 185 nm can still kill germs.
Here's the bottom line when you're selecting germicidal UV products: Make sure you buy the right light bulb for the right fixture and follow product use guidelines.
Advantages of germicidal UV
Germicidal UV lamps are extremely effective and have several major advantages.
- Pathogen kill rate – Tests show that germicidal UV products kill up to 99.9% of bacteria and viruses when used correctly. On top of that, bacteria and pathogens cannot become resistant to UV like they can certain antibiotics and antibacterial products.
- Limited chemical exposure – UV-C works in place of potentially harmful chemicals. It's safe to enter a room after germicidal UV products disinfect the area, but it might be hard to breathe in a room that has just been sprayed down with chemicals.
- Lighting configurations – There are multiple lighting configurations for germicidal UV light, including different types of fixture installation, mobile units, and industrial HVAC attachments. Mobile units are a great option for hospitals, airports, fire and police stations, and the hospitality industry because they're easy to move from room to room. Plus, mobile units are a budget-friendly option compared to installing fixtures in every room.