Feb 10, 2022
More than two years since the onset of COVID-19, answers are emerging about our industry’s tools to combat it

By Dan Litvin

December 2019—the first case of a novel respiratory disease that would forever change the world was identified. The rapid international spread of COVID-19 united researchers, scientists, doctors, technologists, manufacturers, government officials, facility managers and consumers in a unified effort to curb the spread of the SARS CoV-2 virus. Among the most effective technologies to arise was a modern readaptation of a century-old lighting technology. In the two years since the onset of the global COVID-19 pandemic, the UV-C lighting industry has grown to become a multi-billion-dollar industry.

First, a quick primer on UV-C disinfection. UV-C disinfection has been utilized, tested and researched since the start of the 20th century. Historically, UV-C disinfection was utilized primarily in niche applications. In the wake of the COVID-19 pandemic, demand for UV-C disinfection for application in high-traffic facilities has exploded. While the base technologies are not new, innovations to improve functionality and safety have been integrated into three major methods of delivery:

Air Purification – Application of UV-C light directly to circulated air to treat against airborne pathogens is especially effective as this technique can be utilized in occupied spaces to provide active treatment against diseases which are spread via aerosolized particles. Methods of UV-C air purification include applications within HVAC air handling units or ductwork, upper air fixtures, and fixed or portable air purification devices.

Direct UV-C – Application of UV-C light from installed fixtures or portable devices to provide highly effective and rapid treatment against airborne and surface-level pathogens within line-of-sight from the light source. While highly effective, direct disinfection should only be performed in the absence of occupants. Motion sensors to trigger lights off upon detection, timers, automated door locks and remote monitoring systems can be utilized to ensure safe operation.

Hybrid – Installed fixtures and portable devices that provide air purification during times of occupancy and direct treatments while unoccupied.

For a more comprehensive investigation on UV-C light, its technical applications and engineering considerations, please see the article titled “A Deep Dive Into Deep Cleaning” in the October 2020 edition of LD+A, or the pioneering reports from the International Ultraviolet Association at www.IUVA.org.

With that, here are seven things we’ve learned about germicidal lighting since the start of the pandemic:

1 | Improvements to indoor air quality is a major trend that the lighting industry is well-equipped to address.

High-traffic facilities such as offices, schools, apartment complexes and hospitals have emerged as nexuses for the spread of highly communicable airborne viruses like SARS-CoV-2 through close proximity of occupants, build-up of pathogens on surfaces and in the air, lack of proper ventilation, and failure to implement safe and effective disinfection protocols.

For this reason, the pandemic hyper-charged a burgeoning movement toward improvements to indoor air quality, defined by the EPA as “air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants.” Unfortunately, patchwork solutions such as opening windows or increasing ventilation are not always possible or advisable, hiring independent contractors or extra staff for cleaning can be prohibitively expensive, and many alternate disinfection methods have limited effectiveness or produce harmful by-products.

Properly designed germicidal lighting systems provide builders, architects, city planners, facility directors, manufacturers and industry professionals versatile, effective, affordable and safe tools to improve indoor air quality. Air treatments including upper-air and UV-C-HVAC provide powerful yet passive disinfection as to not disrupt normal operation of occupants. Direct UV-C treatments can provide additional surface and air purification without harmful by-products or residues and contain multiple safeguard redundancies to avoid accidental exposure to occupants. Entire germicidal systems can be synced through incorporation into building management systems that provide live monitoring, reporting and extra safety measures.

2 | “UV-C irradiation is highly effective in inactivating SARS-CoV-2 replication.”

This was the title of a study published March 18, 2021, in the journal, Scientific Reports. In this study, “The potential virucidal effects of UV-C irradiation on SARS-CoV-2 were experimentally evaluated for different illumination doses and virus concentrations. At a virus density comparable to that observed in SARS-CoV-2 infection, a UV-C dose of just 3.7 mJ/cm2 was sufficient to achieve a more than 3-log inactivation (99.9%) without any sign of viral replication.”1

These findings, supported by the peer review of researchers around the globe, show that SARS-CoV-2 is more rapidly and effectively treated by UV-C disinfection technologies than previously believed. For reference, findings published by Signify and the Boston University School of Medicine in June 2020 found “a dose of 5mJ/cm2, [resulted] in a reduction of the SARS-CoV-2 virus of 99% (2-log).”2

Dosage is a calculation of UV-C intensity multiplied by treatment time. A smaller treatment dosage means that treatments can be performed quicker and/or less powerful UV-C light sources can be effectively applied. This means that facility-wide applications like HVAC-based systems, upper-air and direct are scientifically proven to be highly effective at disinfecting SARS-CoV-2, as well as the many other pathogens that a century of research has proven its efficacy against. Furthermore, emerging technologies and niche applications like UV-C LED, UV-C disinfection chambers, and even drones outfitted with UV-C lamps can be effective as well.

3 | Other technologies aren’t cutting it.

Uninformed purchases of devices marketed to improve indoor air quality and disinfect against SARS-CoV-2 is an unfortunate side effect of the urgency of the pandemic. New and emerging research shows that many of these technologies including ozone generators, bipolar ionizers and even over- or improper use of chemicals may produce harmful by-products or may not be as effective as stated. As such, there has been community backlash against these technologies in schools and guidance against these systems asserted by governmental agencies.

In order to avoid a similar fate, it is up to the lighting industry to take leadership in thoroughly researching, testing and providing guidance for proper germicidal light applications, as well as educating consumers and professionals on proper utilization. Fortunately, when high quality UV-C products are utilized in properly designed systems, the lighting industry offers possibly the safest and most effective disinfection technology.

4 | Be wary of bad actors in the UV-C industry.

According to the International Ultraviolet Association (IUVA), “There are few accepted standards for equipment designed for the UV disinfection of air and/or surfaces.”3 As such, a slew of ineffective or, worse yet, dangerous UV-Cbased products are being made for purchase from major online and big-box retailers, lighting distributors and electrical supply houses by resellers, importers and non-lighting professionals.

Beyond the ineffective UV-C “wands” that dominate many online retailers, perhaps the most dubiously marketed UV-C product is that of “dual UV-C + ozone disinfection.” While ozone is a potent disinfection agent, it also poses a distinct health danger to the human respiratory system and can break down certain common materials. In truth, these products are created from lamps devoid of cost-adding filters that block the ozone-generating 185nm UV-C range and thereby can be cheaply produced and sold at a hefty markup. This has tarnished the industry and is often used by competing technologies to point out the “dangers of UV-C.”

To help professionals discern between effective and ineffective or dangerous UV-C products, the IUVA has created the excellent guide, “Advice for the selection and operation of equipment for the UV disinfection of air and surfaces” 3 which can be found via www.IUVA.org.

5 | UV-C is safer than realized (but still avoid direct exposure).

Prior to the pandemic, occurrences of direct exposure to UV-C were exceedingly rare. Therefore, few to no studies were conducted regarding the dangers of long-term exposure. With the newfound interest and widespread implementation of UV-C devices, new scientific data has emerged showing that the dangers associated with 254nm UV-C are overwhelmingly limited to those of a topical nature that pass within 24-72 hours. Over exposure to the skin causes topical reddening and irritation, while the eyes can suffer from the unpleasant experience of photokeratitis, also known as welder’s flash and snow-blindness. This is due to the fact that UV-C light at the range of 254nm and especially 222nm does not penetrate sufficiently deep into the skin and eyes to cause significant long-term harm. On the other hand, naturally occurring UV-A (315-400nm) and UV-B (280-315nm) cause long-term damage including potentially cancer by affecting the basal layer of the skin and lens of the eye. Therefore, the OSHA exposure limits for 254nm UV-C light established in the 1980s of 6mJ/cm2 over an eight-hour period remain a sufficient guideline to avoid the short-term effects of UV-C.

This is not to say that direct UV-C implementations can’t be done haphazardly. In February 2021, during a trial run of a UV-C system implementation in the Cobb County School District in Georgia, direct UV-C disinfection devices faultily activated during periods where they were supposed to be inactive. This malfunction drew enough trepidation from officials to cancel the contract meant for widespread implementation throughout the district. Even though the dangers may be passing, they are still uncomfortable enough to require that direct UV-C fixtures should not activate in occupied spaces. The combination of occupancy sensors, timers, safety redundancies, training, vigorous testing and remote monitoring should be utilized to ensure proper usage and operation of systems.

6 | Emerging technologies have improved, but still have a ways to go.

UV-C LEDs aren’t quite there yet. Currently, most UV-C light sources utilize fluorescent-like low- and medium-pressure mercury lamps. Benefits include high UV-C output, affordability, adherence to standard fixture form factors, and achieving UV-C output at 253.7nm which is near the germicidal peak of 260-280nm.

However, just as in more familiar lighting applications, UV-C LEDs are expected to revolutionize the industry. Longer lasting light sources, less power consumption with greater efficacy, precision of wavelength output to the peak germicidal effect, more flexibility in form factor, unlimited switching on and off, negated warmup times, simple retrofit options, and, ideally, a lower price point are among the benefits of LED.

Unfortunately, UV-C LEDs are still an emerging technology. Current problems include prohibitively expensive pricing, overheating issues and lack of UV-C efficacy. While the last year saw significant improvements and incorporation into niche applications, the technology needs further development until it becomes the standard.

Far UV-C. Studies by David J. Brenner of the Center for Radiological Research at Columbia University have shown that UV-C light at 222nm, dubbed Far UVC, retains impressive disinfection potency, especially against coronaviruses, while being unable to penetrate beyond superficial layers of dead mammalian skin or the cornea. 4 While the promises of this technology are immense, applications are still limited due to several notable factors.

Until UV-C LED, especially at the 222nm range, becomes a viable alternative, current applications of Far UV-C are limited to excimer technology. While these light sources benefit from no warmup times and relatively high rates of efficacy, these lamps suffer from short lifespans of only a few thousand hours, have pricey purchase points, are limited in form factor, and are significantly limited in their wattages.

Furthermore, UV-C sources operating at under 240nm generate ozone through photochemical reactions with naturally occurring molecules in the air. As compared to 185nm “dual-use ozone + UV-C” lamps, the amount of ozone generated is significantly lower and can be alleviated by implementations in areas with good air flow via HVAC systems or open windows. Alternately, a cycling of on- and off-time can be utilized to keep ozone within safe exposure limits and provide adequate time for its dissipation before next activation.

For more information on Far UV-C technology, see the comprehensive report published by the International Ultraviolet Association titled Far UV-C Radiation: Current State-of Knowledge 5 which can be found on www.IUVA.org.

405nm isn’t UV-C but may be the future. Research has shown that light at the far end of the visible light spectrum near the border of UV light has anti-bacterial and anti-viral properties. While the difference in disinfection potency can be described as stones vs. rifles, 405nm light has a few benefits over UV-C light.

First and foremost, 405nm light has been shown to be safe for direct and long-term exposure to occupants. Additionally, 405nm LEDs are highly effective and can be incorporated into standard lighting boards. This allows for low-level 405nm light to operate consistently in light sources emitting standard white light. A facility incorporating 405nm into its lighting can benefit from significantly reduced pathogens counts.

7 | The future of germicidal lighting is bright.

From what we’ve learned in the past couple of years, it is an exciting time to be a lighting professional. Our industry is already instrumental in advancing quality-of-life and green building practices, and now the field of germicidal lighting has emerged to lead the battle against pathogens like SARS-CoV-2 and improvements to indoor air quality. While innovations to research, science and technology require constant vigilance and study from professionals, it has been inspirational to witness the industry work together to create safer, healthier and better facilities.


1 Biasin, M., Bianco, A., Pareschi, G. et al. UV-C irradiation is highly effective in inactivating SARS-CoV-2 replication. Sci Rep 11, 6260 (2021). https://doi.org/10.1038/s41598-021-85425-w

2 Signify and Boston University validate effectiveness UV-C light sources: Signify Company website. Signify. (2020, June 16). Retrieved October 4, 2021, from https://www.signify.com/global/our-company/news/press-releases/2020/20200616-signify-bostonuniversity-

3 International Ultraviolet Association. (n.d.). Advice for the selection and operation of equipment for the UV disinfection of air and surfaces. International Ultraviolet Association Inc. Retrieved October 4, 2021, from https://www.iuva.org/Advice- selection/operation-ofequipment-for-the-UV-disinfection-of-air-and.

4 Buonanno, M., Welch, D., Shuryak, I. et al. Far-UV-C light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Sci Rep 10, 10285 (2020). https://doi.org/10.1038/s41598-020-67211-2

5 IUVA Taskforce on Far UV-C Radiation for Disinfection of Air and Surfaces. (2021, May). Far UV-C Radiation: Current State of Knowledge. Retrieved October 4, 2021, from https://iuva.org/resources/covid-19/Far%20UV-C%20Radiation-%20Current%20State-of%20Knowledge.pdf.


Dan Litvin

Dan Litvin

Dan Litvin, Member IES, is the cofounder and president of Pure Lighting Company where he leads research and education on science-backed innovative lighting... More info »