With the ongoing COVID-19 pandemic and possible future epidemics, better tools to fight infectious disease need to be developed to protect our communities and our people. In the past few years, mainly due to the advancements in LED technologies, UV-C light has gained popularity as a disinfectant. This post will explore UV disinfection, its history, effectiveness and uses.
What Is UV Disinfection?
Ultraviolet (UV) disinfection is a method of using ultraviolet light to clean and disinfect air, water, or surfaces. UV light is part of the electromagnetic spectrum with wavelengths of 10-400 nanometres (nm), just below wavelengths visible to humans.
The UV spectrum is divided into three subgroups: UV-A, UV-B and UV-C. You may have heard of UV-A and UV-B from reading sunscreen labels! While UV-A and UV-B are either not at all or just partly absorbed by the ozone layer, UV-C is fully absorbed and no UV-C from the sun reaches the Earth, and so viruses, bacteria and other pathogens have not developed resistance to it. UV-C is known as germicidal UV from of its disinfecting properties. The technology of using UV for disinfection is often called ultraviolet germicidal irradiation, or UVGI for short.
History of UV Disinfection
The history of ultraviolet disinfection goes back to 1877 when Downes and Blunt discovered the ability of sunlight to prevent microbial. About 50 years later, in 1930, the first [analytical bacterial action spectrum] was published by Gates, showing a peak germicidal effectiveness at 265 nm.
A few years later, William F. Wells demonstrated the ability for mercury UV lamps to inactivate airborne microorganisms and in 1937, he successfully used them to prevent an epidemic spread of measles in schools in Philadelphia.
Unfortunately, UV-C technology was then largely abandoned because of the rise of antibiotics and vaccines. The then only available mercury lamps required high maintenance, were expensive and produced ozone, which is harmful to humans. In the 1980s, there was a resurgence of UV disinfection and UV devices were installed in many hospitals. Recently, there have been big advancements in UV-C LEDs (265 nm), which are now low maintenance, reliable and do not produce any ozone, causing another resurgence of UV disinfection.
How Does UV-C Kill Viruses and Bacteria?
Depending on the received dose, UV can inactivate and kill most viruses, bacteria and other microorganisms. The inactivation is caused by their loss of ability to reproduce and multiply. UV-C light does this by attacking their genetic code (RNA and DNA), forming incorrect connections between parts of their DNA and RNA chains and leading to mutations. The peak of this activity, as was discovered more than 80 years ago by Gates, is at 265 nm, exactly where newer UV-C LEDs emit most of their energy. For comparison, older mercury lamps had a peak at 254 nm, resulting in around 20% lower disinfection efficiency.
Generally, viruses are very susceptible to UV-C, bacteria are slightly less susceptible, and spores and fungi are the least susceptible. This is because viruses are the smallest, and therefore have the largest proportion of them exposed to the light.
Can It Protect Against SARS-CoV-2 (COVID-19)?
With the ongoing global pandemic, disinfecting the air around us has become more and more relevant.
A large amount of research has shown that UV-C is extremely effective since it inactivates pathogens in different ways. For example, for all known coronaviruses it has been shown that UV-C breaks the RNA chains rendering the virus unable to reproduce. It also disintegrates the membrane of the coronavirus virion and on top of it all breaks the structure of the famous spike proteins of the coronavirus. UV-C LED manufacturer Crystal IS, whose LEDs our device uses, presents research that demonstrates the effectiveness of germicidal UVC LEDs against SARS-CoV-2.
Another UV-C LED manufacturer has run tests comparing necessary light intensities to inactivate 99.9% pathogens and found that a similar UV-C light dose was needed to inactivate both E. Coli bacteria and SARS-CoV-2 at 265 nm. Further tests have also shown that UV-C light is effective at inactivating SARS-CoV-2 (COVID-19).
How Is UV Technology Used?
It is important to note that direct exposure to UV-C is dangerous for humans. Because of that, UV-C cannot be used directly on or inside the human body for disinfection. That’s why the current applications focus on disinfecting air, surfaces, and water.
UV air disinfection is usually done by ceiling-mounted disinfection systems or by adding UV-C lamps to the building ventilation systems. Thanks to recent developments in UV-C LED technologies more portable applications, such as the Respiray wearable UV air purifier*, are gaining popularity.
Surfaces can also be disinfected by direct exposure to UV-C light. This requires no people or animals to be present nearby, as UV-C light can burn the eyes and skin. As UV-C requires direct exposure, the lamp needs to be moved around the room. This is to avoid any shadows or hard to reach areas not being disinfected.
Finally, UV light is being used to disinfect water globally, in both large water-treatment plants, and residential water purification systems. The residential systems are mainly used in China and India and are not widely adopted in Europe or North America.
Respiray – An Alternative To Ordinary Face Masks
At Respiray, we believe in using UV disinfection to eliminate viruses, bacterias and other infectious diseases. That’s why have developed a wearable UV air purifier that creates a clean air zone around the wearers face while keeping the face and the mouth of the wearer unobstructed to talk and smile freely.
Our UV disinfection chamber has been shown to disinfect over 99% of viruses and bacteria at 30 litres per minute throughput. Compared to ordinary masks, our wearable air purifier is also more sustainable and environmentally friendly, as it is completely reusable, while medical masks should be thrown away after a few hours or use.
Is Respiray’s Wearable Air Purifier Safe?
Yes, of course. Our device is fully light-sealed, which means that no UV light can escape from our device. Also, our device doesn’t produce any ozone. The LEDs in our device emit a very narrow range of UV-C light at 265 nm, which will produce no ozone. Furthermore, at wavelengths of 242-315 nm, ozone is broken back into oxygen molecules instead, reducing the ambient ozone in the air.
Stay safe and healthy!
We hope you enjoyed reading about the history of UV light and how it has been used as a disinfectant for over 100 years. If you have any further questions about our device and its effectiveness, then please don’t hesitate to contact us.