Disinfect building spaces with light

Philadelphia Business Journal Leadership Trust

By Billy Hodges , Founder at Digital Filaments 

Billy Hodges is Founder & President of DIGITAL FILAMENTS
Architectural + LED Lighting and a life-long student of lighting 

Light can kill germs and will likely be an integral part of disinfecting buildings in the future. In general, it tends to be more environmentally friendly than chemical cleaners, and some versions of disinfecting light can be implemented safely and effectively in your building.

Building owners should consider installing permanent fixtures that incorporate normal lighting for working as well as disinfecting light. These fixtures should be installed over high-touch surfaces and in frequently shared spaces prior to inviting employees back full time following the COVID-19 pandemic.

There are several different types of disinfecting light that can kill germs or pathogens (viruses, bacteria, mold, etc.) that can make us sick. It’s important to know that all of these technologies kill some percentage of the germs. Therefore, the question becomes, “How much of this specific light technology do I need to kill enough germs to matter? Specifically, “What is the dose of each type of light that I need to kill the germs that concern me?”

Specific intensities of specific wavelengths applied for specific amounts of time create these “doses” of light. There are three types of commercially available disinfecting lighting technologies.

Indigo blue light (405nm)

Indigo blue light has been around for some years and is generally considered safe for humans when used correctly (except for the nausea risk in a portion of the population). It has been used fairly regularly in locker rooms, gyms and some hospital applications. 405nm indigo light is somewhat effective against some germs (including some bacteria and mold), but it’s less effective against viruses. It’s visible light, which means we can see that it is on when it’s working. Given that this light is both visible and deep blue, it’s generally undesirable for use when people are performing most tasks — especially those in which it’s important to be able to see other colors.

Ultraviolet A (365nm)

365nm UV-A is invisible and can be integrated into standard-looking white light fixtures. It’s been proven to be an effective “continuous disinfection” technology and has been researched extensively for use in buildings and around people. UV-A is more effective than indigo for killing many types of germs and, when used in appropriate low doses, may be safe for humans.

Hospitals, in particular, have studied the use of UV-A on high-touch surfaces to kill many nonviral hospital-acquired infections (HAIs), including germs like E. coli, staph and MRSA. Studies have found it likely to be safe in environments such as the NICU, with appropriate radiation restrictions in place.

UV-A is the part of the ultraviolet spectrum that is transmitted through the atmosphere. The doses of UV-A used for continuous disinfection are very low and not dangerous to people: A typical 24-hour UV-A fixture dose is equivalent to only minutes of bright sun.

Ultraviolet C (254nm)

254nm UV-C is a long-established lighting disinfectant technology and is much more powerful than indigo or UV-A. Germicidal UV-C kills bacteria, mold and viruses quickly, including the SARS family of viruses.

The main trade-off for using UV-C is that it is not safe for humans to be in the space while it is in use for disinfection purposes. This leaves building tenants and owners with a choice about how to apply it safely. It can be mounted on the wall and aimed toward/across the ceiling in a strategy called upper air disinfection (which keeps the UV-C light away from the humans but also does not disinfect the surfaces below). It can be integrated into air handlers, killing germs as the air cycles through the ducts (but not the room surfaces). It can be rolled on a cart from room to room on a regular schedule (but this is labor-intensive and only disinfects while in that room). It can also be integrated into the architectural lighting and controlled with sensors and timers to ensure that it is not being utilized while people occupy the space.

There’s also far-UVC, which is a newer technology that deserves much more testing. Inital research shows that it may be as effective as germicidal UV-C but as safe as UV-A. If this proves to be true, it could be the best of both worlds.

Owners should consider incorporating permanent light fixtures with a disinfection circuit to augment their chemical disinfection strategy. Killing germs automatically between chemical disinfections can provide a significantly safer workplace for your employees.

Billy Hodges is Founder & President of DIGITAL FILAMENTS Architectural + LED Lighting and a life-long student of lighting.