Research and Review: Using UV Light to Disinfect

June 23, 2020
Lighting Design

In the era of COVID-19, an increasing number of markets are exploring the use of UV light disinfection. Here, we explore the benefits and risks of this developing technology.

The discussion about and application of ultraviolet light disinfection technology is not new or revolutionary. Education and medical facilities have a long history of successfully using UV light as a disinfection and sterilization tool; however, as is always the case with developing technology, the fabric of this conversation is changing and we as a design community have a responsibility to familiarize ourselves with the benefits and the risks.

In the era of COVID-19, an increasing number of markets are exploring the use of UV light disinfection for more than just the sanitization of masks and other medical equipment. As we move forward in our exploration of this technology, we need to first establish what this article is and what this article is not. This article is not meant to be a comprehensive design guideline nor is it meant to be a resource that has all the answers. This article is designed to provide information to designers so they can gain a well-rounded overview of the current research from a fresh perspective. After reading this, my hope is you will:

  • Better understand the implications of UV, germicidal UV and 405nm lighting as it relates to bacteria and proper application in interior spaces.

  • Feel empowered to confidently and knowledgeably discuss the available technology, including the risks and benefits of this technology, with clients and partners.

  • Be able to competently discuss this technology with manufacturers and ask informed questions when it comes to UV-enabled products to ensure the safety of all future occupants.  

As with any highly scientific and specific technology, designers must do their own research to understand how to safely integrate UV light disinfection in a variety of environment types.

Defining Key Terms and Debunking Common Misconceptions

The electromagnetic spectrum is the tool by which we measure electromagnetic radiation and is made up of everything from gamma rays (think the radiation that turned Bruce Banner into the Hulk) to more commonly used microwaves and radio waves. Wavelength is one way we measure along the electromagnetic spectrum: increasing from left to right, short wavelengths found on the left side (gamma side) of the spectrum are considered most harmful to humans; as wavelengths increase, the risk to biological lifeforms decreases.

Wavelength is one way we measure along the electromagnetic spectrum: increasing from left to right, short wavelengths found on the left side (gamma side) of the spectrum are considered most harmful to humans; as wavelengths increase, the risk to biological lifeforms decreases. Image courtesy of GE Current.

Gamma is the shortest wavelength on the visual spectrum. The most common applications of this type of electromagnetic radiation are found in non-contact industrial sensors, the sterilization of medical equipment and nuclear research. Xrays are probably the most recognizable radiation on the electromagnetic spectrum. Used most commonly in medicine as a tool for viewing broken bones and other internal issues, the use of X-rays has allowed for powerful advances in healthcare.

Ultraviolet is likely also widely recognized, though not as widely understood. This is the type of electromagnetic radiation that makes black-light posters glow and is responsible for summer tans. For the purpose of this article, we’ll focus on UV as it relates to the visible light spectrum. First, let’s review the four main types of UV light:

  1. Vacuum UV (below ≈ 200 nanometers) refers to the wavelength range where a vacuum apparatus is often used because the light is strongly absorbed in the air (most often used in medical equipment).

  2. Short Wave (UV-C) also known as “germicidal UV” is the most harmful to humans and does not occur naturally in our environment (this UV is filtered out by our ozone).

  3. Middle Wave (UV-B) is harmful to humans and less commonly found, though is emitted by the sun and present in our environment. This is the UV most associated with various cancers.

  4. Long Wave (UV-A) is the most common type we encounter. It is emitted by the sun and relatively harmless during limited exposure; long-term exposure (e.g. the kind that causes sunburns) can lead to health complications.

The visible light spectrum accounts for all the visible light we see on Earth. It comprises a relatively small amount of the electromagnetic spectrum and ranges in color from violet to red, and from about 400 nanometers (nm) to 700nm. The blue light portion of this spectrum (also known as harmful blue light) can be found at the left end of the visual spectrum consistent with shorter wavelengths approaching 400nm. New LED technology suggests a particular part (405nm) of the visual light spectrum can be employed for its anti-microbial qualities.

The visible light spectrum accounts for all the visible light we see on Earth. It comprises a relatively small amount of the electromagnetic spectrum and ranges in color from violet to red, and from about 400 nanometers (nm) to 700nm.

When talking about UV lighting and its applications as a “cleaning” tool, it’s important to understand what we mean when we use certain phrases. Some commonly used (and misused) words found in these conversations include the following, which are each defined by the CDC:

  • Sterilization: Sterilization describes a process that destroys or eliminates all forms of microbial life and is carried out by physical or chemical methods.

  • Disinfection: Disinfection describes a process that eliminates many or all pathogenic microorganisms on inanimate objects.

  • Decontamination: To decontaminate is to make an object or area safe by removing, neutralizing or destroying any harmful substance. Basically, decontamination is what happens as a result of the processes of sterilization or disinfection.

Not all the above terms apply to all types of UV light, so it’s critical to understand the intended result and associated risks based on these definitions before employing any “germicidal” or other antimicrobial lighting techniques. Let’s debunk the mystery surrounding UV light disinfection by exploring some commonly held misconceptions about UV light:

  • Misconception #1: “UV light kills everything.UV-C, also known as the germicidal UV, is proven to kill1 many bacteria and pathogens, including some variations of coronavirus linked to the flu. It has not, however, been shown to have the same effects on COVID-19. Studies are currently underway to understand the full breadth of effectiveness for shortwave UV-C and it’s important to note that this type of UV is considered non-discretionary, meaning it will not discriminate against good or bad bacteria. As humans, we are host to many good bacteria that help keep us healthy and functioning; exposure to UV-C is highly dangerous for all forms of biological life and should be used with a high level of caution and discretion. UV-C is only one small branch of UV; understand the results desired to better be able to specifically tune in the correct wavelength of UV for the application.

  • Misconception #2: “Indirect UV light is less harmful.” All UV, though not located on the visible spectrum, does have reflective qualities and will bounce off reflective surfaces similar to other light sources. As such, reflected UV light can be just as harmful to humans. Any exposure (direct or indirect) poses a risk and should be applied thoughtfully and with caution.

  • Misconception #3: “UV light is only outside.”It is true that the sun is the main contributor of UV light and that UV light is most prominent in outdoor environments. With artificial light and other modern conveniences, however, UV sources can be found just as often in many common interior applications such as fluorescent office lighting and tanning beds. Understanding our light sources and putting in the research can help promote healthy interior spaces with high-level design.

  • Misconception #4: “UV light is damaging to eyes and skin.” Different types of UV wavelengths come with different levels of threat to human biology. We experience exposure to UV on a daily basis; small amounts of specific wavelength UV light help to promote our growth and overall health. Make no mistake, UV can be damaging to ALL biological systems; but, levels of damage vary with the type of UV, length of exposure, intensity, and distance.

Though it’s helpful to understand, and thereby debunk these common misconceptions, a critical component of the application of UV is to always proceed with caution. Do your own research by digging deeply into scientific studies and white papers, some of which I’ve included at the end of this article.  

Uses of Ultraviolet UV and Other Antimicrobial Lighting

All wavelengths of UV light have been proven to have disinfecting qualities, though different types of UV light have varying degrees of effectiveness and ability when it comes to disinfection and sterilization. As technology develops and our society adapts to new social structures, work-life balances and how these constructs interface with biological threats, it’s becoming increasingly critical to understand the intent of and innovations around UV light as a protective measure.

UV-C is the only known germicidal UV, meaning it’s the only UV known to immobilize (killing1) a wide variety of the bacteria, germs and viruses commonly found in our environment. While it’s the most common type of UV used to disinfect, it’s also the most harmful to humans and therefore cannot be used while humans are present.

405nm light is a relatively new (less than 10 years old) technology that will soon be saturating the marketplace. 405nm, which appears violet in color, is found at the left end of the visible light spectrum closest to UV and falls before blue light. This light method has been proven to inactivate certain microbes associated with healthcare-associated infections, the types of infections patients can get while receiving healthcare for another condition (e.g. staph or MRSA infections). New information and studies may suggest this wavelength in the visible spectrum is more harmful than we thought and could lead to long-term negative effects. Critical things to note when exploring 405:

  • It needs further research. The long-term effects on humans are not yet fully understood with this technology. 405nm is found on the shortwave end of the visible spectrum, which is known to have some harmful side effects in relation to the human eye and body. New studies may suggest lighting of the 400nm wavelength may be more harmful than originally thought. While more research is being done it is important for designers to stay up-to-date on the current studies and information being released.

  • It does not replace regular disinfecting methods, but rather should be used in conjunction with these practices. While new technology still requires research, one thing is for certain: so-called clean5 lighting is not a replacement for existing disinfecting and/or sanitizing methods. Germicidal and antimicrobial lighting should be used as an additional measure of prevention alongside current standards for cleaning.

  • It is not germicidal with limited abilities. To date, 405nm light has no known effects on viral pathogens, viruses or certain strains of harmful bacteria. While it’s known to affect commonly found bacteria such as staph and MRSA, 405nm light is not germicidal and should not be considered as such.

  • It is undetectable during occupation. Lights equipped with this technology emit a purple type of lighting not unlike blacklight in appearance; though it does not exhibit the same visual effects of blacklight lamps. Some fixtures are equipped with dual circuits allowing occupants/employees to turn on and off the disinfectant LEDs; other fixtures run a lower level of disinfectant LED alongside the standard white LED, which results in delivered white light with a purple undertone. Designers should be cognizant of this potential color shift in their designs as it will likely affect the overall aesthetic of the space.

Applications of UV Light in Healthcare

A common application of UV light in healthcare facilities is known as “upper-room germicidal ultraviolet.” Systems employing this technique are designed to focus concentrated UV-C light in the upper part of a room (typically above 7FT), thus inactivating airborne infectious agents in the air and filtering down into the space below. While the lower part of the room is meant to be kept relatively UV-C free, minimizing exposure to persons below, indirect sources still pose a risk to occupants by way of reflected light. Surfaces and finishes matter in these applications to ensure occupant safety, it’s best to study the reflective qualities of all surfaces in the affected area. The intent is to provide indirect UV light to inactivate any airborne bacteria as the air filters down.

Education and medical facilities have a long history of successfully using UV light as a disinfection and sterilization tool, including systems designed to inactivate airborne infectious agents in the air. Fairfield University School of Nursing and Health Studies by RDG. Photo by Robert Benson Photography.

A more direct method of applying germicidal lighting consists of UV-C light towers, which are rolled into a room to disinfect the space after it’s been vacated. The towers are operated while the room is unoccupied and people are prohibited from entering the space during this process; occupancy-enabled safety features also ensure the tower’s deactivation should someone accidentally enter the space. While effective, this way of germicidal lighting still has its flaws: UV light disinfection is only applicable in places the lighting has “touched,” thus areas under the bed, inside drawers/cabinets and other cracks or crevices are still at high risk for infection; and, because the room must be unoccupied during disinfection, facilities may lose critical bed space for potential patients.

There is much to be learned when it comes to using light in new and innovative ways. It’s not yet sufficient to say that UV or 405nm light is successful and a best practice, but it would likewise be inappropriate to discount studies that show their effectiveness. As more studies are concluded and new information surfaces it’s vital that modern designers stay vigilant and informed to be able to best make decisions about the future of the spaces they create.

Tips and Tricks for Doing Your Own Research

Manufacturers of this lighting technology are required to produce “white papers” to ensure the safety of these products in human environments. These papers are scientific studies and are available upon request. Designers should request this information and study these papers to ensure proper application and safe implementation of any technology within their designs.

While the internet and other news articles can be informative and are easier to digest, it is important to compare the information with scientific studies and professional agencies. Referencing a variety of sources is the best way to be sure you are getting accurate information from diverse perspectives. Also, be aware of the condition under which studies and case studies are conducted to correctly analyze solutions and their applicability to designed spaces.

Additional UV Lighting Resources

Scientific Studies

  • Wang Y., Wang Y., Wang Y., Wang Y., et al. (2017). Antimicrobial blue light inactivation of pathogenic microbes: State of the art. Drug Resist Update, 33-35, 1-22. Accessed at: /pmc/articles/PMC5699711/

  • Gwynne, P., Gallagher, M. (2018). Light as a Broad-Spectrum Antimicrobial. Frontiers in Microbiology, 9, 119. Accessed at: /articles/10.3389/fmicb.2018.00119/full

  • Ramakrishnan, P., Maclean, M., MacGregor, S., Anderson, J., & Grant, M. H. (2016). Cytotoxic responses to 405 nm light exposure in mammalian and bacterial cells: Involvement of reactive oxygen species. ScienceDirect, 33, 54-62. Accessed at: /science/article/pii/S0887233316300273?via%3Dihub

  • Hiraku, Y., Ito, K., Hirakawa, K., Kawanishi, S. (2007). Photosensitized DNA Damage and its Protection via a Novel Mechanism. Photochemistry and Photobiology, 83(1), 205-212. Accessed at: /doi/full/10.1562/2006-03-09-IR-840

  • McKenzie K., Maclean M., Grant M.H., Ramakrishnan P., MacGregor S.J., Anderson J.G. (2016). The effects of 405 nm light on bacterial membrane integrity determined by salt and bile tolerance assays, leakage of UV-absorbing material and SYTOX green labelling. Microbiology, 162(9), 1680-1688. Accessed at: /pmc/articles/PMC5068139/

Illuminating Engineering Society Committee Reports


  1. Kill in the context of this document refers to the inactivation of some or all of the functionality of certain proteins or bacteria resulting in cellular death or the inability of the microorganism to harmfully affect biological life.

  2. “Clean” in reference to lighting techniques, refers to any method of disinfecting or sanitizing by way of light. Including but not limited to germicidal UV-C, UV-A, UV-B and 405nm.

Written by Shelby Hunter, Lighting Designer