You are already cleaning surfaces, but did you know there is a way to disinfect the shared air in your space? Keep reading to learn more about UVC and coronavirus, and how you can prevent airborne pathogen transmission in your facility with technology proven effective for over 100 years.
As we continue to deal with the Covid-19 pandemic, reopen schools and large facilities, head into winter flu season, and enter an era in which even more pandemics may potentially occur in the years ahead, everyone is thinking about how to mitigate the risk of catching coronavirus. So we turn to the CDC recommended guidelines for cleaning and disinfecting against Covid-19 and hope for the best. What most people don’t realize though, is that the EPA N list only includes chemical disinfectants. They don’t routinely review things that aren’t chemicals, and so a very important germ-killing technology that has been trusted for over 100 years is potentially being overlooked.
UV-C germicidal light.
What is UV-C?
Ultraviolet light is invisible to the human eye. It is electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays.(1) Most people are aware of UV-A and UV-B, since those are what reaches the earth’s surface and what we protect ourselves against when we wear sunscreen. UV-C is a range of UV radiation that is almost completely blocked by the ozone layer of the atmosphere, so it mostly isn’t found on the Earth’s surface. It is a short-wave, “hard” range of UV and is found in the 100-280 nanometer range.(2)
How Does UV-C work (and can it kill coronavirus)?
UV-C light inactivates microorganisms by damaging their genetic material (DNA) and rendering them unable to replicate.(3) A range of wavelengths on the UV-C spectrum are effective at killing germs, but the peak germicidal effect is right around 265 nm.(4) UV-C radiation is effective at inactivating bacteria, archaea, fungi (yeasts and molds), algae, protozoa, and viruses including SARS-CoV-2, the virus that causes Covid-19 disease.(5)
Is UV-C lighting safe?
UV-C disinfecting systems are very safe when designed, installed, and maintained regularly by trained professionals and handled with care by knowledgeable operators.
Skin and Eyes
While UV-C is the most biologically active kind of UV radiation, it is also considered to be the least dangerous to humans. This is because UV-C radiation is only absorbed by the outer, dead layer of human skin, while UV-B and UV-A radiation penetrate deeper. Therefore, the long-term health risks are negligible compared with common solar UV exposures.(6)
It is not completely risk-free however. Direct exposure to open UVC lamps, especially those emitting longer wavelengths, can cause skin and eye damage, so safety must be implemented in the design of the system to ensure that humans aren’t directly exposed. (For this reason, the use of consumer-grade handheld UV wands is highly discouraged.)
UVC lamps can also degrade certain materials such as plastics, polymers, and textiles, so lamps need to be placed in an appropriate location to avoid being too close to susceptible materials. Also, some UV-C bulbs contain small amounts of mercury, so those should be handled with care and EPA guidelines for cleanup followed if broken.(7)
There are a few different types of lamps that can produce UVC radiation and they each generate different wavelengths of UVC.(8) However, it is important to note when selecting which kind of UVC lamp to use for a particular application, that UVC radiation below 242 nm will produce ozone. Ozone is a powerful and highly reactive gas that can be a helpful cleaning tool, but is also a strong respiratory irritant. (9) So currently, most UV lamps for germicidal lighting applications will generally be ones that emit wavelengths of 240 nm and higher. (Fun fact: wavelengths above 240 nm inversely destroy ozone and create oxygen!).(10) An exception of course is in the case of ozone generators, which are produced by purposefully housing 185 nm UV lamps and a fan inside a chamber.
Another exception is Far-UVC. Far UV-C is UV light with a wavelength of approximately 222 nm. This is proposed to be the best wavelength to penetrate bacteria and viruses, but not penetrate skin very much if at all. (11) So in theory, humans could be more safely exposed to the open lamps and benefit from surface disinfection plus surface-level skin disinfection with a lower risk of eye and skin damage. Promising research has proven that in addition to the longer wavelengths, 222 nm Far-UVC will effectively kill coronavirus at the appropriate dose. More testing needs to be done though, in part because of the ozone production potential. (12)
History of UV-C
The first article documenting claims that sunlight could destroy bacteria showed up in 1877. Great strides in the science were made in the coming decades and by the early 1900s, medical applications of UV light were being more widely utilized. A scientist named Niels Finsen even won a Nobel prize in 1903 for his work in UV phototherapy after successfully treating patients who had lupus vulgaris, a painful and disfiguring skin infection, by using UV light. However, the use of phototherapy eventually declined, because a new germ-fighting tech came on the scene.
The antibiotic era lasted close to 50 years and revolutionized the treatment of infectious disease. It wasn’t until the 1970s and 80s, when antibiotic and chemical-resistance was starting to become an issue, that interest in UV light started to reemerge. Research in the water treatment and ventilation systems was of particular interest, and today we see UV disinfection in commercial settings such as hospitals, water treatment plants, and more. (13)
How Can I Use UV-C in My Facility?
There are a number of UVGI system options available which are designed to either disinfect the air or disinfect surfaces. At Energy Lighting Services, we follow the IES guidelines and ASHRAE guidelines and recommend Upper Room UVGI systems as the primary means for reducing airborne infectious diseases (including coronavirus) via UV lighting in most facilities.
Upper Room UV-C systems are the safest and most effective (more effective than HVAC UV systems), and can be used while rooms are occupied to actively clean the air at all times.(14)
Upper Room UV-C luminaries are wall or ceiling-mounted and continuously irradiate large volumes of air in the area of a room below the ceiling and above the heads of the occupants. These fixtures are equipped with louvers that angle the beam of UV light upward and shield the lower room and protect the occupants below. Ideally, rooms with Upper Room UVGI should have good air mixing (via HVAC ventilation and/or low velocity fans), humidity between 30-60%, and a temperature between 68-75 degrees Fahrenheit.(15)
Upper Room UV lighting does the most of all UVGI systems to prevent person-to-person transmission of airborne pathogens.