UltraViolet: An Ultra Grime Fighter

Ultraviolet Light

Architectural lighting design is focused on using visible light to make a physical space appealing and functional.  Lighting designers spend our time applying the right light to enhance the environment and provide long term value to the project owner.  If there is one thing we have learned from Covid-19, it is future design strategies of the built environment will likely change.

People are social creatures. The inability to eat out, go to work or school and see friends takes a toll on our mental health.  We need cleaning and disinfectant strategies to restore our faith in the ability to safely patronize retail, restaurants, entertainment venues, and a host of other physical places.  Fortunately, ultraviolet light can come to the rescue.

Ultraviolet light is not part of the visible light spectrum but resides between visible light and x-rays.  UV is present in daylight and divided into three basic groups.  UV-A is considered a long wave between 315 and 400 nanometers and is the chief instigator of a sunburn, which is why it is a good idea to wear sunscreen.  Anyone over the age of 10 knows you can get a sunburn without even knowing it being outside too long without sun protection.

UVB is a medium wave between 280 and 315 nanometers and is mostly absorbed by the ozone layer.  It is important for us to be good stewards of the planet because an intact ozone layer allows us to enjoy all sorts of outdoor activities (applying sunscreen, of course) that contribute to our health and wellbeing.

The real superhero in our story is UVC, the shortest wave at 100 and 280 nanometers.  This is also called germicidal UV and is absorbed by the ozone.  When used properly UVC is an effective grime fighter in the war on viruses and bacteria.  The very characteristic that makes UVC such a good disinfectant also makes it genetically harmful to humans and life on earth, so it must be used with caution.

Mechanical air systems have long had the capacity to incorporate UVC in air filtration systems but mechanical engineers may not talk about it much.  The International WELL Building Institute™ knows all about the importance of UVC to control microbes and mold in the Air Concept.

If an owner is considering using UVC to disinfect a space, careful planning should be done with professional expertise in specifying UVC systems along with attention to room scheduling and occupancy.  Humans should not be exposed to UVC directly and it should only be used in unoccupied spaces.

Bacteria versus Virus

Bacteria are living organisms and are everywhere, including inside and outside your body.  Some are good for you and some make you sick which is why we want to eliminate the bad actors.  In addition to natural and chemical disinfectants, light can also kill bacteria.  Light just inside the visible spectrum at 405 nanometers has been shown to be effective at killing bacteria such as Salmonella, E.Coli, Staph, and others and is generally safe for use around humans.  We are exposed to 405 nanometers in daylight.   A mixture of 405nm specific light spectrum with other general lighting does create a color shift, like making the lens purple,  so it is recommended that samples are reviewed by the design team along with furniture, millwork, and paint finishes to make sure there are no surprises during construction.  It might even be a good idea to inform customers that light is being employed in the space as a disinfectant.  That could help by reassuring customers the business cares about them.

Viruses are a different animal altogether.  They are not living organisms, but are an infectious agent that multiply within a living host.  Light in the visible range of 405 nanometers does not kill viruses, so we must rely on UVC and disinfectants to do this work.

Looking Forward*

In light of the Covid-19 pandemic, architecture and design can take the lead in developing priorities and directing solutions to protect the public and private spaces that we so desperately want to use.   Engage partners who can provide services and products to employ anti-microbial LEDs, germicidal UV, or both, and let’s all stay safe together.


*Since this article was originally published in May 2020 studies have surfaced regarding the use of 222nm as a means to neutralize viruses.  These studies are encouraging because the very short wavelength does not penetrate human skin to damage DNA and are still effective as a disinfectant.  We continue to urge caution when employing any UV system.  Proper PPE and safety measures should be followed according to manufacturers’ guidelines.