In the 1890s, scientists experimenting with sunlight and filters discovered that a narrow band of the visible light spectrum (400–405 nanometers, associated with violet) was effective at killing bacteria.
The idea of applying light energy as a germicide is not new. Used in hospitals and similar applications, ultraviolet (UV) light is a powerful germ killer. With this type of germicidal lighting, the space is saturated with UV light for several minutes to an hour, which can significantly reduce germs. However, exposure is harmful to humans. For this reason, the space must be vacant while it’s being used.
Using visible light from LEDs, visible light disinfection (VLD) provides functional illumination that is safe for humans, while containing recipes for saturated blue/violet emission that is harmful to germs. It has been commercialized by companies like Kenall Manufacturing (Indigo-Clean) and Vital Vio, Inc., which licenses to Visa Lighting, Evolution Lighting and others.
The advantage of VLD is that it continuously disinfects, including during times the space is occupied. While the germicidal effect is slower and not as powerful as UV, manufacturers claim a high level of disinfection can occur over an entire day for certain types of organisms, notably “superbugs” such as MRSA.
Applications include any in which bacteria, mold and fungi must be minimized, ranging from healthcare to athletic facilities to restaurants, and where it is typically combined with intermittent cleaning. The most obvious are hospital emergency rooms, operating rooms and similar healthcare applications where VLD is often combined with UV and manual cleaning for maximum germ reduction. Hospitals are very concerned with pathogens, as 1.7 million Americans each year acquire an infection while in a hospital, which may delay recovery or be life-threatening, according to the Centers for Disease Control.
“Visible light LED disinfection technology is a continuous—not instantaneous—disinfection approach,” said Colleen Costello, co-founder and CEO of Vital Vio, Inc. “It is intended to be used in conjunction with traditional, intermittent disinfection methods. Each enhances the other.”
In the healthcare market, VLD luminaires are typically specification-grade, sealed, enclosed, recessed healthcare luminaires designed to produce visible light saturated with the desired wavelengths. Common sizes include 2-by-4, 2-by-2, 1-by-4, etc. In other markets, the technology may be implemented using recessed downlights, task lights and other luminaires in addition to troffers. Theoretically, any LED luminaire type can be adapted to produce a VLD effect.
These luminaires install similarly as non-VLD luminaires and interact with many of the same controls. No special staff or training is required to operate the luminaires. However, designing for VLD illumination requires paying special attention to manufacturer instructions. A sufficient amount of light must fall on room surfaces, which requires the right quantity, output and placement of luminaires for the application.
Additionally, the VLD luminaire may offer a special mode of operation in which it does not turn off during vacancy but instead transfers to a concentrated spectral emission for continual disinfection. This requires occupancy sensors (if installed) to be carefully applied so the operating mode changes only during periods of vacancy, and users are not inconvenienced by the color of the light changing.
Finally, the VLD luminaire should carry appropriate ratings for lighting performance (light output, visual comfort, etc.), electrical/safety and application (UL/ETL, IP64/65, NSF2, etc.) and IEC 62778 for blue light hazard.
Because VLD luminaires cost 25–100% more than typical LED luminaires, the business case is typically based on the economic value of avoiding infection rather than energy cost savings. With infection avoidance, a different economic scale comes into play, as these costs are so much higher than energy costs. If even a single infection can be avoided over the product’s 10-year life, this can result in a very short payback based on that cost reduction alone.
“Because visible light disinfection is safe for people and equipment, it can be applied across a broad range of applications where infection prevention is valued,” said Cliff Yahnke, Ph.D., Kenall Manufacturing’s director of clinical affairs for Indigo-Clean. “The business case for VLD is best made in those areas where the risk of infection is highest.”
Typically, the owner will require it, though there may be an opportunity for contractors and distributors to propose it based on knowledge of the product and the research supporting it. Contractors considering a proposal of VLD lighting should request research used to substantiate claims. Otherwise, they may benefit from familiarizing themselves with any special requirements for projects in which they are tasked to apply and/or install VLD luminaires.
Enabled by the more easily customizable spectral emission characteristics of LED lighting, visible light disinfection provides healthcare and other organizations a new option to potentially strengthen their infection control protocols.