Different types of light disinfection have been around for decades, but with the introduction of COVID-19 and the resulting pandemic, the need for efficient and comprehensive disinfection has spiked. Today, the interest in ultraviolet-C (UV-C) radiation has never been higher. Leading health and safety organizations, including the Centers for Disease Control (CDC), have recognized the efficacy of UV-C radiation. Studies show that ultraviolet radiation light can be an effective way to destroy the outer protein coating of the SARS-Coronavirus and many other types of bacteria and viruses. Destroying the outer coating ultimately leads to the inactivation of viruses.
But UV-C radiation does more than destroy COVID-19 organisms. It is also a known disinfectant widely used to sterilize air, water, and nonporous surfaces. In fact, UV-C radiation has been used for decades to effectively reduce the spread of a range of dangerous bacteria, including tuberculosis.
What is UV-C Radiation?
For much of the twentieth century, health care professionals have been warning people about the adverse effects of long-term exposure to UV radiation from the sun. This type of solar radiation is comprised of ultraviolet A (UV-A), ultraviolet B (UV-B), and ultraviolet C (UV-C). UV-C is potentially the most dangerous type of ultraviolet light, but this type of UV ray cannot penetrate the ozone layer, so it is not usually present in the earth’s atmosphere.
German scientist Johann Wilhelm Ritter is credited as the first to identify UV-C in 1801. As early as 1845, it was known that microorganisms could be destroyed with light waves. Still, it wasn’t until tuberculosis (TB) surged in the 1980s that serious efforts were made to harness the protective properties of UV-C radiation. In 2005, the CDC began to fully endorse the use of UVGI (ultraviolet germicidal irradiation) to control the spread of TB in healthcare settings. In 2009, the CDC started to issue official guidance documents for using upper-room UVGI to prevent the spread of dangerous bacteria and viruses in healthcare settings.
How Do Manufacturers Make UV-C Radiation Safe for People?
UV-C radiation is very effective at inactivating viruses but also can be unsafe for humans. To counter this potential danger, scientists have worked on ways to safely use this light in heavily occupied spaces.
Upper-Room UVGI Zones
The CDC recommends upper-room radiation as part of a layered strategy that combines multiple prevention tactics such as consistent and correct use of masks, ventilation, physical distancing, cleaning and disinfection, and hand hygiene.
Creating upper-room UVGI zones encourages disinfection above people in the rooms they occupy. HVAC system, fans, or open windows keeps air moving throughout the room. Airborne pathogens are killed as they pass through the disinfection zone and are exposed to the appropriate amount of UV energy. These particles remain in the air, but they are inactivated, so they are no longer infectious.
Similar to the upper-layer strategy, in-duct radiation keeps air and pathogens moving through the ductwork, exposing them to UV-C radiation in the passages. People are not exposed to the light, and therefore it poses no health threat.
Empty Room Disinfection and Motion Detection
Some manufacturers offer UV-C lights that can be used when a room is vacated. This approach is often applied in tandem with motion detectors that serve as safety features to automatically disable UV-C lights if any motion is detected.
Use of Far UV-C and Near UV-C
Broad-spectrum UV can include a combination of UV-A, UV-B, and UV-C wavelengths. Broad-spectrum UV is very effective at disinfection, but direct exposure is dangerous to humans. Many manufacturers that use this type of light recommend installing it in ductwork or using occupancy sensors that disable the light when motion is detected.
Far UV-C light, a narrow spectrum of ultraviolet light, has been shown to be effective at killing some types of bacteria without harming humans. Far UV-C is a smaller segment of the UV-C spectrum and refers to wavelengths between 207 and 222 nm. This type of light has a very limited range, so it can’t penetrate the dead-cell outer layer of human skin or the tear layer in the eye. But because viruses and bacteria are much smaller than human cells, far UV-C light can reach their DNA and inactivate them.
Near UV light is safe for humans and kills many types of germs. Therefore, it is often used as part of a light disinfection system that combines the use of different wavelengths that change when people are in or out of a room. Near UV, or UV-A, typically falls between the wavelengths of 300 to 400 nm.
Considerations for Efficacy
There are many types of lights on the commercial and consumer market that claim to disinfect. However, there are well-recognized limitations to the effectiveness of UV-C radiation to inactivate viruses. Before considering a UV-C radiation system, it’s essential to understand the parameters of the technology.
(1) Direct Exposure is Required.
A virus must be exposed directly to the radiation to be inactivated. If a surface has traces of soil, dust, or fluids, this may prevent the light from inactivating viruses.
(2) Time and Intensity Matter.
It’s critical to understand how much light is needed to disinfect an area. More intense lights with longer exposures are required to increase efficacy.
(3) Spectrums’ Efficacies Vary.
UV-B and UV-A radiation are less effective than UV-C radiation at inactivating the SARS-CoV-2 coronavirus. UV-B presents significant dangers to humans. UV-A radiation is less hazardous but is also 1000 times less effective than either UV-B or UV-C radiation at inactivating the SARS-CoV-2 coronavirus.
(4) Factor in Dangers.
Exposure to UV-C light or looking at UV-C light can damage skin and eyes. Exceptions exist for far-UV and near-UV, so it’s critical to understand which type of light is in use.
Want to Include UV-C Capabilities in Your Project?
Coward Environmental Systems, Inc. is proud to represent manufacturers of UV-C light products for projects in the Philadelphia region, Central PA, Delaware, and Maryland. Contact us today to discover how SLD Technology can be a part of your next project.