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Environmental disinfection methods involving ultraviolet (UV) light have been found to be highly effective against significant microorganisms, but they can differ in something known as UV dose. The following is a closer look at UV doses and their effects.
What is UV Dose?
Ultraviolet light – also known as UV light – is a form of radiation found on the electromagnetic spectrum. UV light has wavelengths that range from 100 to 400 nanometers (nm) and unlike visible light, can not be distinguished by the unaided human eye.1
UV light comes in different forms, but UV-C light, with a wavelength of 200 to 280 nm2 is especially noted for its association with:
- Fungi
- Mold
- Spore
- Bacteria disinfection3
UV-C light with wavelengths of 254 nm is also sometimes referred to as Ultraviolet Germicidal Irradiation, or UVGI. UVGI’s effects on bacteria and its surroundings is not always uniform, however, this depends on something called UV dose.
UV dose is defined as the amount of UV radiation projected from all directions onto the surface of an extremely small sphere, divided by the area of a cross-section of that sphere.4 5 Also known as fluence, UV dose can be expressed in terms of millijoules per square centimeter (mJ/cm2).
Since the effects of UV doses are measured in relation to exposure times, UV dose units are often multiplied by exposure time, represented by t.6 Generally, the greater the exposure time, the more profound the effects of UV dose will be on microorganisms and environmental materials.7 8
UV Dose Effects
When it comes to using UVGI in the realm of environmental disinfection, UV doses affect their surroundings in two significant ways.
Firstly, a UV dose has been associated with an impact on microorganisms in a given environment. Secondly, depending on exposure times, UV doses can affect environmental materials as well. Both of these effects can differ considerably between static and autonomous UVGI disinfection methods. 
UVGI has been associated with microorganism reductions:
- on surfaces9
- in liquids
- as well as in the air
UV doses have been applied with significant impact on epidemiologically significant microorganisms such as: - Escherichia coli (E. coli)10
- Staphylococcus aureus
- Candida Albicans, and
- Clostridium difficile
Higher UV doses have been associated with generally higher rates of disinfection.11
Environmental UV dose effects, however, do appear to correlate with exposure times. As an example, though treated wood surfaces are invariably resistant to UV degradation, untreated wood specimens can experience cell wall thinning after 10 days of UV dose exposure – with an elimination of portions of the wood’s secondary cell wall after 30 days.12
Though this particular scenario is not common in indoor UV disinfection practices, it does illustrate the potential of UV doses to affect certain materials over time. This, however, can be mitigated through use of mobile, autonomous UV disinfection solutions.
UV Doses and Autonomous Disinfection
UV disinfection methods for indoor environments can include use of either static or mobile, autonomous (or self-navigating) methods. Methods that involve static disinfection tools typically consist of a free-standing unit that emits UV light in a room over long periods of time.13 These methods typically prolong a room’s exposure to a UV dose, and increase the chances for material degradation.14 15
Autonomous UV disinfection methods, however, typically involve machines that are self-driving and emit UV doses to many areas in a disinfection session. As autonomous units are highly mobile when compared to static machines, they typically can expose environments to UV doses for comparatively much shorter durations.19 This limits the chances of potential material degradation provoked by prolonged UV dose exposure.16
UVD Robots for Disinfection
UVD Robots (short for Ultraviolet Disinfection Robots), are self-driving UVGI disinfection robots pioneered by Blue Ocean Robotics, a Danish company that specializes in developing professional robotic solutions.
As autonomous units, UVD Robots are self-navigating and highly mobile, reducing the risk of prolonged UV dose exposure to indoor environments. They are additionally capable of reaching shadowed areas of rooms, and, in comparison with their static counterparts, able to cover greater distances for disinfection.
These robots have also been associated with eliminating microorganisms at elevated efficacy rates.17 They are capable of emitting UVGI associated with eliminating microorganisms, at a 4-log reduction, or a rate of 99.99%.18
In conclusion, UVD Robots provide an efficient reduction of UV dose exposure times, and offer better rates of disinfection efficacy. This technology works with an understanding of UV doses and environments, to provide higher efficacy in disinfection.
Explore the Power of UVD Robots: Download Declaration overview on UV Disinfection Effectiveness
