In early 2020, design and construction teams had to respond quickly
to the spreading SARS-CoV-2 virus, including figuring out how to keep safely working as an essential service in a time when guidance seemingly changed daily. Immediately, disinfecting wipes and hand sanitizer were in short supply, leading distilleries to market hand sanitizer while other manufacturers marketed lighting products for killing viruses. This article will help to filter the claims of virus-killing light.
Just like purchasing a vehicle and then realizing how many people have that same vehicle, writing an article about germicidal ultraviolet (GUV) products and practice made the authors realize just how many GUV products are available for purchase and already deployed. While standing in a socially distanced line at a hospital, reading the email giving the go-ahead on this article topic, one of the authors looked up to see a banner highlighting the integration of a UV-C disinfecting light into a check-in kiosk. Since then, there has been a steady flow of forwarded emails from co-workers shocked at the unsubstantiated advertisements of virus-killing light they have received and mentions from friends and family of the products they have seen or have been asked to use.
The broad availability of products that claim to use light to kill viruses and other pathogens may give consumers a sense of confidence, but it may be a false sense of confidence. The reason for the proliferation of these products is in part due to a lack of standards, which are critical to enable consumers and end-users to compare product performance and make informed decisions. The lack of standards also makes it easy for claims to be made—with little accountability. Vigilance is needed when implementing GUV to avoid wasting money or, more seriously, causing injury.
GUV: WHAT IS IT?
Ultraviolet wavelengths are segmented into UV-A (315 to 400 nanometers [nm]), UV-B (280 to 315 nm), UV-C (200 to 280 nm) and vacuum UV (100 to 200 nm). Slightly overlapping the ultraviolet region is the visible light region, approximately 380 to 780 nm. There is some potential for using the violet portion of the visible light region for disinfection; however, it requires a combination of greater duration and intensity than UV-C. Here we’ll focus on the application of UV-C to inactivate pathogens, including bacteria, mold spores, fungi and viruses.
Low-pressure mercury lamps have been in use for nearly a century for disinfection purposes, and they are still the most commonly deployed and efficient UV-C source. These lamps resemble familiar fluorescent lamps but are constructed with specialized quartz glass and without the phosphor coating that shifts fluorescent lamps’ UV discharge to the visible light region. Solid- state ultraviolet sources, such as UV LEDs, do exist, yet considerable improvements still are needed to match the performance of low-pressure mercury.
Deploying GUV requires careful design to make sure the right spectrum and amount are hitting the target surface over a given period of time. For the SARS-CoV-2 virus, researchers are still working to understand the spectrum most effective for deactivating the virus. The effectiveness of GUV is proportional to the wavelengths used and the exposure dose, which is a product of source output, area irradiated and time. Without careful design and installation, many GUV products can be a waste of money at best, or worse, can result in acute injuries and/or lead to an unwarranted relaxation of manual cleaning efforts and overall caution.
GUV: WHY and HOW?
Before the COVID-19 pandemic, health-care-associated infections (HAIs)—for example, developing a bloodstream infection during a hospital stay—were already a serious problem and GUV was being studied as a potential solution, particularly for antibiotic-resistant infections. According to the Centers for Disease Control, on any given day, one in 31 hospital patients has an HAI. Hospitals combat HAIs in a variety of ways from handwashing to standardized manual cleaning and verification protocols. Some facilities use GUV disinfection procedures to further reduce pathogen transmission.
Although the use of GUV products in health care is a relatively established practice, there is likely to be increasing adoption of GUV products and practices in the coming years in response to the COVID-19 pandemic. Upper-room air disinfection systems use GUV to treat air at approximately 7-feet above the finished floor and higher, keeping the UV-C above head height. A key component is the circulation of room air via ceiling fans or other systems to keep air moving through the upper portion of the room. GUV can be permanently integrated into mechanical ductwork to deactivate airborne pathogens or plumbing systems to address waterborne pathogens; these are alternative applications with a reduced risk of exposure to building occupants. GUV can also be integrated into portable devices for room surface disinfection. For example, a portable unit may be wheeled into intensive-care unit patient rooms and operating rooms after the patient is discharged. These units are left for a period of time to inactivate surface pathogens that are within line of sight; importantly, pathogens lying in the shadows of GUV emissions are not deactivated.
GUV applications require careful maintenance and attention; incorrect use can result in eye and skin injuries that could become cancerous over time. It is easy for failed lamps to go unnoticed or the wrong replacement lamps to be installed. Safety sensors and timers can malfunction, and the presence of children and pets may go undetected by sensors. Regardless of the application, it is important to educate and implement protocols that prioritize safety.
Another consideration when implementing GUV is the types of materials within a space. Room surfaces absorb UV-C, potentially causing damage to these surfaces ranging from relatively benign, such as fading of fabrics, or, more seriously, it can cause material to degrade to the point of creating another safety concern. This is more commonly witnessed with daylighting—the ultraviolet (UV-A and UV-B) portion of the daylight spectrum causing materials to fade and some plastics to become brittle.
Although there are many reasons for caution when implementing GUV, there are also many case studies, papers and reports outlining how to use it safely. One of the most common uses of UV-C radiation prior to 2020 was for minimizing the spread of tuberculosis in health-care settings. In 2009, the CDC’s National Institute for Occupational Safety and Health (NIOSH) published a report providing detailed guidance for upper-room ultraviolet radiation for tuberculosis, a disease usually transmitted via airborne particles. Since 1997, NIOSH studies have consistently shown that properly designed and maintained upper-room air disinfection systems can deactivate and kill tuberculosis. And it isn’t all about the UV-C. Air circulation, humidity and temperature are all key to the effectiveness of these systems.
GUV: WHERE ARE THE STANDARDS?
There are presently no industry standardized methods of measurement to characterize the performance of GUV products, leaving manufacturers to employ their own largely proprietary methods for measuring spectrum and intensity, thereby making comparisons between products very challenging. Consequently, the presence of a product safety label, like UL, may only mean the product has been tested for electrical safety. (Note: It is good practice to verify the authenticity of any safety label.)
Thankfully, the standards void will begin to be filled later in 2021. Experts with the Illuminating Engineering Society and the International Ultraviolet Association are collaborating to publish industry standardized methods for taking accurate and repeatable ultraviolet measurements, enabling product comparison between manufacturers. The first of these American National Standards published by IES will be methods of measurement for the sources themselves, including low-pressure mercury lamps and UV LEDs. A great resource for learning more is the IES Committee Report 2-20-V1, Germicidal Ultraviolet (GUV)—Frequently Asked Questions.
It may be surprising that the adoption of GUV in the U.S. has remained relatively low given it has been around for nearly a century, but it was also not that long ago that many transitioned away from the century-old incandescent light sources for illumination. The reignited interest in GUV is leading to new research, technology and products, giving designers and engineers new opportunities to improve the spaces where we work and live.
IMAGES: Pacific Northwest National Laboratory