Over the past couple of years, the awareness around UVC light has increased manifold. While there have been several research studies conducted on the efficacy of its wavelength and its disinfection properties, it is only in 2020 that the investigations in this field started gaining momentum due to the onset of the coronavirus pandemic. The situation is also compelling scientists to explore possibilities within the existing technology for disinfection in occupied spaces that has put focus back on upper-room ultraviolet germicidal irradiation systems.

Although there has been a looming concern around the use of UV technology for disinfection purposes and for its human safety aspect, it has been found that upper-room UV technology can be safely used in the presence of living beings.

What is Upper-room UVC Disinfection? How does it work?

Upper-room UVC refers to a system of ultraviolet germicidal irradiation (UVGI) luminaire fixtures that emit UVC light (100-280 nm) for disinfection purposes. Such systems are usually installed in the upper part of a room to destroy harmful pathogens from the air and create a more hygienic environment.

Air disinfection is the primary purpose of upper-room UVC devices. Various studies suggest that for these devices to work effectively, they should be installed at an approximate minimum height of 7 feet measured from the bottom of the fixture to the floor. They work by projecting UVC light across the upper room space. While that happens, various microorganisms like bacteria & viruses present in the air get transported towards the ultraviolet field by convection currents, where they are rendered inactive by the UV light, and finally get destroyed. The process is further explained in the image below.

(Image depicting upper-room UVC disinfection)

Elaborating further on Upper Room devices, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), in one of its studies says “Upper-air (also commonly called upper-room) devices are installed in occupied spaces to control bioaerosols (e.g., suspended viruses, bacteria, fungi contained in droplet nuclei) in the space. In-duct systems are installed in air-handling units to control bioaerosols in recirculated air that may be collected from many spaces, and to control microbial growth on cooling coils and other surfaces. Keeping the coils free of biofilm buildup can help reduce pressure drop across the coils and improve heat exchanger efficiency (therefore lowering the energy required to move and condition the air), and eliminates one potential air contamination source that could degrade indoor air quality. UVC is typically combined with conventional air quality control methods, including dilution ventilation and particulate filtration, to optimize cost and energy use”.

Since upper-room UVC is installed far from direct human contact, it is believed to minimize the chances of UV-related exposure and thus, can be safely used in occupied rooms.

Upper-room UVC and Human Safety

While it is true that the current pandemic has brought the Upper-room UV technology to the forefront, its effectiveness and subsequent safety in containing the spread of airborne diseases such as Tuberculosis is being tested since many years now. A Tuberculosis Ultraviolet Shelter Study (TUSS) published by the US NationalLibrary of Medicine in 2008 is one such example. The study was conducted at 14 homeless shelters in six U.S. cities from 1997 to 2004. The shelter inhabitants were asked to fill up a questionnaire and answer if they faced any eye or skin irritation while being present in a room that was being disinfected by upper-air UVC system.

The study found that “careful application of upper-room UVGI can be achieved without an apparent increase in the incidence of the most common side effects of accidental UV overexposure”.

Application of Upper-room UVC in Healthcare

The use of upper-room UVC disinfection devices have been commonly seen in hospitals and healthcare facilities in an attempt to reduce cases of healthcare-associated infections (HAIs), since it minimizes airborne transmission of disease-causing germs in such enclosed spaces. To render it more effective, some establishments often install upper-room UVC near coils and drain pans of air-conditioning systems.

According to an indoor air quality report titled ‘Using Ultraviolet Germicidal Lights for Air Cleaning’ published by Berkeley Lab, “UVGI systems can also be installed in the ducts of heating, ventilating, and air conditioning (HVAC) systems and irradiate the small airborne particles containing microorganisms as the air flows through the ducts”. The report further explains how the projected UV light inside ducts can significantly reduce growth of mold and bacteria that are commonly found on the wet surfaces of drain pans and cooling coils.

Nowadays, upper-room UVC technology is not limited to just hospitals, but gradually being adopted in other establishments and facilities as well. Let us explore some of its latest application areas.

Other application areas of Upper-room UVC Disinfection

Laboratories: As the place that allows scientists and researchers to come up with practical solutions to most of our problems, laboratories seem like the natural choice along with healthcare in terms of application of upper-room UVC. It is also where one can effectively investigate the germicidal properties of such UVC devices in a controlled setting. According to a section in the American Journal of Respiratory and Critical Care Medicine, “In laboratory tests of an upper room UV system (five fixtures and a total of 216 W), the room average concentration of culturable airborne bacteria was reduced on UV exposure by between 46 and 98% compared with the original concentration, depending on the room ventilation rate and microorganism”. The report also stated that the results were consistent with previous works conducted in this field, and further proved the effectiveness of upper-room UV germicidal systems, even in complex real-world settings. 

Educational institutions: Educational institutions throughout the US have been some of the most active adopters of UV-based sanitizing and disinfecting devices to reduce the risk of students and staff contracting harmful illnesses, especially during the pandemic. While it was reported that Chester County’s Lewisville Elementary participated in a pilot program to use GUV sanitization technology within its premises, other institutions like Penn State are doing their part in creating a disease-free learning environment. The University is working on a research to explore the efficacy of upper-room UVC in classroom disinfection. Even Dr.Edward A. Nardell, a professor of global health and social medicine at Harvard Medical School has shared his views on the importance of upper-room UVC. He was quoted by The New York Times as saying “We have struggled in the past to see this highly effective, very safe technology fully implemented for airborne infections. We’ve done the studies. We know it works”.

 Upper-room UVC can be installed with upper air-conditioning vents as seen in a Lecture hall

Homeless Shelters: As the Tuberculosis Ultravioltet Shelter Study quoted above reported, the application of upper-room UVC disinfection system has been proven to be effective in enclosed spaces like homeless shelters. Since such spaces can often be crowded, the importance of air disinfection is greater in order to minimize the chances of infectious agents getting transmitted from person to person. This has further been backed by the ASHRAE report that stated, “Settings appropriate to upper-air UVC placement include congregate spaces, where unknown and potentially infected persons may share the same space with uninfected persons (e.g., a medical waiting room or homeless shelter)”.

Prisons: Prisons are often considered to be some of the most unhygienic establishments in the world. Wherever there are issues with hygiene, there’s bound to be diseases as well, like tuberculosis. However, with upper-room UVC technology, such establishments can lead to better and cleaner environment for inmates. According to a research published on GHD Online, which is a joint initiative by Brigham And Women's Hospital and Harvard University, such systems can be used to reduce airborne transmission in indoor spaces, “such as hospital clinics, homeless shelters, and jails, where undiagnosed, but infective, cases are apt to be present”.

Apart from the aforementioned application areas, upper-room UVC disinfection devices can also be used in various other enclosed facilities, such as manufacturing units, food processing plants, veterinary facilities, restaurants, etc. Now that we have understood what upper-room UVC is, its process, and its application areas, it can be looked at as an effective solution to creating germ-free indoor spaces. With all the research studies, experiments and pilot programs backing the technology, it seems like upper-room UVGI is ready for a wider implementation to disinfect air of harmful particles.