The COVID-19 pandemic has created a renewed focus on ensuring that workplaces, facilities and public spaces are safe to use. Interest has since turned to ultraviolet lighting as a tried and tested means of disinfecting air, water and surfaces.
In this article, we give an overview of what UV lighting actually is, how it works and where it can be applied.
The science of it all
UV light is that part of the electromagnetic spectrum that spans 100-400 nanometers (nm). Basically, it is divided into three different types, A, B and C.
UV-A and UV-B is found in sunlight. It’s what gives you a suntan or sunburn. UV-B is well known for medical applications, such as the treatment of psoriasis, and is also responsible for the formation of bone-strengthening vitamin D.
Then there’s UV-C, which is an invisible light, spanning the range of 100-280 nm, and has powerful germicidal properties. UV-C from the sunlight is filtered out by the Earth’s atmosphere. We should be thankful for this as exposure to certain wavelengths of UV-C radiation is hazardous to the skin and eyes of humans and animals. Despite this, UV-C lighting, when designed properly, installed correctly with safety instructions followed, is a safe and highly effective form of disinfection.
Proven track record
For years, UV-C has been used to disinfect drinking water, wastewater, air, pharmaceutical products, and surfaces against a whole suite of pathogens. In fact, it has rendered inactive all bacteria and viruses tested to date (many hundreds over the years, including coronaviruses).
Let’s review the various forms of disinfection
1. Surface Disinfection
Disinfection of surfaces is performed through direct exposure to the UV-C radiation from lamps, luminaires or disinfection carts that are activated when people are not present. They can be brought into a workplace when people have left. An extra level of safety may be provided by remote on-off switches and sensors which can shutdown systems if people or animals are detected.
Typical surface disinfection lamps are 55W and depending on the dose, disinfection can be done in seconds or a matter of minutes.
Of course, the light won’t be able to reach areas in shadow. So, for areas requiring deep disinfection it is recommended that UV-C forms part of a multi-barrier approach, alongside traditional scrubbing and cleaning with chemical disinfectants. Where UV-C scores highly is that it saves on time, requires few to no people and no chemicals. Surface disinfection lends itself to high contact areas such as offices, schools, restrooms and gyms.
2. Air Disinfection
Contaminated air, at an upper level, passes through a ‘UV-zone’ where it’s disinfected. Such systems can be used in rooms with people present as the light source is shielded from those below and located at a height of at least 2.3m.
Some air conditioning systems also us UV-C where high output lamps will keep the cooling coil free from microorganisms that can otherwise stick together to create a biofilm. In addition, UV-C lamps may be applied inside air conditioning ducts to inactivate bacteria. Due to the high air speed, the required UV-C dose inside ducts will be relatively high.
3. Water Disinfection
Applications include disinfecting and purifying drinking water, wastewater, process water, swimming pools, and ponds. UV-C lamps are available in numerous wattages depending on the application, which varies from large municipal installations in which several hundred lamps are used, to small units that fit inside household sinks to disinfect drinking water.
A technology whose time has come
The COVID-19 pandemic has put UV-C lighting firmly into the spotlight. Today, companies and institutions are waking up to a new normal where germ and virus-free spaces are no longer ‘nice to haves’. UV-C lighting, which has been around for more than 40 years, is a well-tested, yet relatively unsung technology. It has taken a terrible pandemic for it to emerge out of the shadows. A technology whose time has surely come.
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