Visibly Clean

By Parker Allen

Supreme Court justice Louis Brandeis famously said, “Sunlight is said to be the best of disinfectants.” He wasn’t actually talking about sunlight and disinfection, but rather the importance of transparency. But, his quote was correct in the literal sense. Sunlight, and other illumination sources, can be potent disinfecting agents when used safely and appropriately.

First, a brief primer on light. Visible light is one narrow portion of a much broader spectrum of light – the electromagnetic spectrum. Light travels at a constant speed. It varies in terms of frequency and wavelength, which are inversely proportional to one another. The higher the frequency, the shorter the wavelength, and vice versa. Frequency is directly proportional to the energy of the light wave, so the higher the frequency, the more energetic the light. Only energetic enough to cause atoms to vibrate and rotate, visible light(380-700nm) is classified as ‘risk exempt’ per IEC62471.* Conversely, containing enough energy to knock electrons off atoms and ionize molecules, all ultraviolet light (180-380nm) is assigned a risk designation per IEC62471, based on the hazards each poses to human health.

*The International Electrotechnical Commission (IEC) standard: Photobiological Safety of Lamps and Lamp Systems, developed to protect people from photobiological damage caused by LED light.

The electromagnetic spectrum

Photo credit: earthsky.org

Recently, Chelsea High School in Chelsea, Michigan, completed a new auxiliary gym project, including a 6,500 square-foot weight room. Weight rooms are famously a breeding ground for all sorts of pathogens, including dangerous bugs like methicillin-resistant Staphylococcus aureus (MRSA). Students are in close contact with one another, breathing heavily, and touching shared surfaces. High school students don’t exactly have a reputation for great hygiene. So, the decision-makers in charge of the project felt the need to include germicidal lighting in the weight room. They worked with Kenall Manufacturing to install eighty 55W MLHA5 Series fixtures with Kenall’s Indigo-Clean™ Technology.

This technology harnesses the disinfecting properties of 405nm light to continually disinfect the space. It has been demonstrated to be effective against a range of pathogens, including SARS-CoV-2, influenza-A, and MRSA. 405nm light is in the visible portion of the light spectrum, between blue and violet. Because it is visible, it doesn’t present the documented risks that UV light does. It is safe to be in the room while the disinfecting light is on. Although slightly less efficacious than UV, it is appropriately dosed based on the dimensions of the space.

Kenall Manufacturing’s Millenium Stretch germicidal LED luminaires installed in the Chelsea High School weight room not only illuminate the space but also kill harmful germs.

Indigo-Clean™ technology in use at Chelsea High School’s weight room. Exercise facilities have been considered “high-risk” for transmission of harmful bacteria because of their enclosed environment, shared equipment and close contact between users and staff. Clinically proven to reduce harmful bacteria, 405nm lighting technology can be installed to provide continuous disinfection.

Cliff Yahnke, Chief Scientist and Head of Clinical Affairs at Kenall, pioneered the technology. He explained, “Ultimately, what we did was build a clinical basis of evidence, which established a level of disinfection in medical settings. And from there, that methodology is applied to non-clinical settings like a classroom or weight room.” The required dose to provide disinfection for the weight room was calculated and then distributed across the fixtures, so the relight is accomplished using a one-to-one replacement of the existing fixtures. Because the Indigo-Clean™ technology blends seamlessly with other white fixtures in the space, installation was easy.

When the weight room is occupied, the fixtures are in “White Disinfection Mode,” providing blended white light and 405nm indigo light from LEDs. The fixtures are controlled via an occupancy sensor. After 20 minutes of no movement, they switch over to “Indigo Disinfection Mode,” turning off the white light and routing all the power into the indigo light in order to ramp up the disinfection. Speaking about Chelsea School District’s decision to go with visible light disinfection, Yahnke explained, “They feel like they can do something beneficial without introducing a hazard to the room.”

“I’ve worked in many school districts over the past 12 years, but this is the first time I’ve encountered these lights. They’re a welcomed addition for disinfecting and cleaning, and I hope we can add them to other rooms throughout the district’s schools,” explained Ron Mills, Chelsea School District’s Director of Operations, shortly after the project was completed. Since then, Ron’s wish has been granted, as there are plans underway to add the fixtures to two other schools in the school district.

Since the beginning of the pandemic and the disruption it caused to our lives, there is a lot of talk about disinfection technology, and for good reason. Germicidal UV remains the most popular disinfection method using light, but this technology represents a safer alternative that might make more sense in certain circumstances. “All disinfectants are optimized around some set of tradeoffs; this is optimized around safety,” explained Yankhe. Both GUV and visible light disinfection have their advantages and their drawbacks. When approached by a customer asking about disinfection technology, you need to weigh your options and figure out which lighting disinfection product is right for the project. ■