Craig’s Lighting Articles, Products + Technology

Disinfecting with Light

Below is my contribution to the February issue of tED Magazine, the official publication of the NAED. Reprinted with permission.

Hospitals and other healthcare buildings are designed and operated to minimize the chance of infection. The growth of superbugs—pathogens that are difficult to kill with current drugs—is of particular concern. According to the Centers for Disease Control (CDC), each year, 1.7 million Americans contract a hospital-acquired infection, which can delay recovery or even be life-threatening, resulting in about 100,000 deaths.

Besides using disinfecting chemicals, another approach to disinfection is to saturate a space with ultraviolet (UV) light. While UV light is highly germicidal, it is also dangerous to humans. For this reason, UV light is intermittently applied when the space is unoccupied for periods ranging from several minutes up to an hour, resulting in a dramatic reduction in germs but also enforced periods of vacancy.

In the late nineteenth century, scientists experimenting with sunlight and filters discovered that a narrow portion of the visible light spectrum (400-405 nanometers) could be used to kill bacteria. Recently, advances in LED technology made this concept practical, resulting in commercialization. Today, patents are held by Strathclyde University, which licenses its technology to Kenall Manufacturing (Indigo-Clean), and Vital Vio, Inc., which licenses to Visa Lighting, Evolution Lighting, and others. Visible light disinfection (VLD) luminaires have spectral emission recipes saturated in these blue-violet wavelengths, enabling human vision while being destructive to certain germs.

Portion of the electromagnetic spectrum showing ultraviolet wavelengths, which are effective for germicidal use but harmful to humans, and the blue-violet portion of visible light, which is less germicidal but safe for humans. Image courtesy of Indigo-Clean/Kenall.

“Harnessing the germ-killing capacity of visible light disinfection provides the new option of continuous disinfection, which is safe for human and pet exposure,” said Colleen Costello, Co-Founder and CEO, Vital Vio, Inc. “Used in combination with traditional intermittent cleaning, our company’s technology is proven to eliminate up to 90 percent of bacteria and other harmful organisms growing on surfaces.”

The claimed advantage of VLD is it continuously disinfects, particularly when the space is occupied, as occupancy inherently poses a higher risk of pathogen transmission. Though not as germicidal as UV and ineffective for sterilizing equipment or purifying water, VLD technology can be effective against a wide range of pathogens on surfaces, including the superbugs MRSA and C. diff. For this reason, for optimal results, VLD may be combined with UV and chemical disinfection, as it is designed as a complement, not a replacement, for an existing disinfection program.

“In general, UV light is good for applications in which a high amount of disinfection is needed in a short period of time,” said Cliff Yahnke, PhD, Kenall Manufacturing’s Director of Clinical Affairs for Indigo-Clean. “Visible light works slowly but more continuously, and can achieve similar levels of disinfection for certain organisms over an entire day. The key to using each is to understand the types of organisms that need to be eliminated in the desired space, the time available or needed for this enhanced disinfection, the tolerance for operational disruption, and the ongoing costs—labor, training, maintenance, consumables, etc.—beyond the initial capital purchase.”

VLD technology is available in common specification-grade healthcare luminaires such as sealed, enclosed recessed luminaires (2×4, 2×2, 1×4, etc.) as well as recessed downlights. However, any luminaire used with LED technology can be adapted for a disinfection function, such as task lighting. The luminaires install and light a room similarly as non-VLD luminaires and are compatible with many of the same control devices. Additionally, they require no special staff or training to operate to produce the VLD effect.

That being said, to gain the VLD effect, the manufacturer may have specific instructions on application, as a sufficient quantity of light must reach room surfaces based on the number of luminaires and their output and layout. Further, the VLD luminaire may offer a second mode of operation, in which it does not turn OFF during periods of room vacancy but instead switches to a concentrated blue-violet (germicidal) emission for continual disinfection. This requires proper application of occupancy sensors so that the operating mode changes only when the room is unoccupied.

Common applications include operating rooms, emergency departments, pharmacies, procedure/exam rooms, and patient bathrooms. Potential applications include those where bacteria, mold, and fungi are problematic, which may include athletic facilities, restaurants, senior facilities, etc. The VLD luminaire should provide the desired level of lighting performance (light levels, visual comfort, etc.) while having the appropriate ratings (UL/ETL, IP64/65, NSF2, IEC 62778 for “blue light hazard,” etc.).

Visible light disinfection luminaires designed to operate in an alternative mode in which all visible light output is turned OFF during room vacancy except for blue-violet output, enabling continuous disinfection. Image courtesy of Indigo-Clean/Kenall.

The business case for specifying the luminaire with VLD increases based on the risk (and cost) of infection. Distributors should ask suppliers to substantiate claims with appropriate research, make light dosing recommendations for achieving an appropriate germicidal effect, and validate that the luminaire otherwise will be suitable for the application based on its performance ratings.

“VLD is a paradigm shift for electrical distributors as the fixtures cost substantially more—25 to 100 percent—than a standard fixture,” Yahnke said. “This cost, however, is easily addressed through the prevention of a single infection. Therefore, distributors should work with their contractors and customers to reach the facility owner where the benefits of the technology can be fully realized. They should stress that the avoidance of just a single infection over a 10-year life span of the VLD system represents a 2.2-month payback on the cost of the entire system.”

“As electrical distributors become aware of lights that multi-task to disinfect and illuminate, they can differentiate themselves by educating their clients about the benefits of this protective technology,” said Costello. “Equally important is making sure electrical contractors know to not value-engineer disinfecting lighting products out of a lighting specification. Disinfecting luminaires do cost more than single-purpose illumination-only fixtures, but are specified for particular locations because of the added benefit of the germ-killing capability. Sometimes, electrical contractors don’t know or understand that they can’t simply swap out these fixtures with a similar-looking, single-purpose, less-expensive fixture.”

Overall, visible light disinfection represents another new application made economical with LED technology, providing healthcare and other organizations an option to potentially strengthen their infection control programs.

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Craig DiLouie


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