UVC LED Surface Disinfection

UVC LED FAQ's

• What systems do you have ready to use?

  Visit our UVC LED Curing Systems Page for information on our range of UVC Solutions. We have the COBRA Clean FX1 available in 265nm for test. We will have other wavelengths and form factors available very soon. Please contact us directly to find out about our roadmap.

• Can your systems sterilize?

  Our systems can be utilized for sterilization but the lamps effectiveness is largely dependent on the environmental conditions in which they are operating and how it is designed. ProPhotonix has more than 25 years of experience partnering with OEMs to develop innovative, reliable LED systems tailored to their specific application needs. We work closely with our partners to understand their application requirements and our multidisciplinary team of LED experts designs and manufactures high-performance LED solutions optimized for their application. Our aim is to deliver a competitive advantage for our customers.

• What research have you done on the effectiveness of UV LED on viruses and bacteria?

  ProPhotonix is a partner in a consortium that was awarded an EU Horizon 2020 grant to develop innovative reactor solutions for disinfection of water utilizing UVA and UVC based LED technologies. The consortium comprises three universities; University of Cambridge (UK), Rey Juan Carlos University (Spain) and Ulster University (UK) as well as two other partner companies; Delft IMP (Netherlands) a designer and manufacturer of nanostructured catalysis materials and FCC Aqualia (Spain), a global water management company. ProPhotonix’s role in the project is to deliver a number of UV LED based systems for these applications. More details can be found at https://www.prophotonix.com/wp-content/uploads/2020/03/ProPhotonix-UV-LED-Water-Disinfection.pdf

• Can I treat a room with your systems?

  Yes. UVC LED systems can be designed to treat a room. ProPhotonix has more than 25 years of experience partnering with OEMs to develop innovative, reliable LED systems tailored to their specific application needs. We work closely with our partners to understand their application requirements and our multidisciplinary team of LED experts designs and manufactures high-performance LED solutions optimized for their application. Our aim is to deliver a competitive advantage for our customers. 

   

  Ref. https://www.lightbulbs.com/blog/how-led-lights-are-making-hotels-cleaner

   

• Is UV LED disinfection effective against COVID 19?

  Preliminary research utilizing UV-C LEDs to combat SARS-COV is encouraging. UV LED manufacturer Seoul Viosys and SETi’s Violeds Technology proves 99.9% sterilization of Coronavirus (COVID-19) in 30 Seconds.  Meanwhile, PuroLighting working with Dr. David Brenner from Columbia University confirmed that UVC light can be effective for combating SARS-COV. Additional studies are now needed to determine and confirm the specific dose response required to inactivate COVID-19 on different surfaces and materials.

   

  Ref.

  1. 1. https://news.columbia.edu/ultraviolet-technology-virus-covid-19-UV-light
     2. https://www.ledsmagazine.com/directory/led-packages/uv-ir-leds/press-release/14173253/seoul-semiconductor-seoul-viosys-and-setis-violeds-technology-proves-999-sterilization-of-coronavirus-covid19-in-30-seconds

• What are the key issues in using UV LED for these applications?

  

  Ref. Lawal, O., Pagan, J. Hansen, M. 2017. When Will UV-C LEDs be Suit-able for Municipal Treatment? Conference Presentation. IUVA World Congress. 18 September 2017.

  UV-C LEDs are a relatively new technology. As can be seen from the chart above, UVC LED efficiency low, below 10%. However, UVC LED development is following a similar rapid improvement profile that has occurred for other LED technologies such as red, blue and UV-A wavelengths.

  Low efficiency also means that the lifetime of these LEDs is less than more mature LED technology. However, for some wavelengths, 10,000 hrs have been reported.

  As applications are still being developed and LED manufacturers improve their processes, LED unit costs continue to reduce. However, the pricing is still not at the level of more mature LED wavelengths and commercially viable applications are limited for the next 3-5 years. As a result of the COVID-19 pandemic, there has been increased interest in UV-C LEDs which may increase this timeline.

• What other factors impact the effectiveness of the system? e.g. time, shadowing

  The presence of particles can protect microorganisms from UV, for example, UV is not effective in highly turbid water due to low transmissivity. 

  UV products cannot penetrate particles like dust or oils, so dirty surfaces will cause effectiveness to drop. 

  Some microorganisms have built up some immunity to UV. Therefore, a higher dose of UV must be deployed to kill these microorganisms. Indeed, the type of microorganism targeted can impact results. For example, 265nm is considered the optimum wavelength to use for disinfection but 275nm has been shown to disinfect E. Coli. 

  Microorganisms cannot be affected if they are not exposed to the light.  Any area where a shadow occurs from an obstacle not allowing the UV light to shine will have no effect on the organism.

  Ref. Li X, Cai M, Wang L, Niu F, Yang D, Zhang G. Evaluation survey of microbial disinfection methods in UV-LED water treatment systems. Sci Total Environ. 2019;659:1415-1427. doi:10.1016/j.scitotenv.2018.12.344 

• What characteristics of the light are important?

  Wavelength, Irradiance and time are the most important factors. 

  Wavelength: UVC wavelength range is between 100nm to 300nm.  Generally, UV-C germicidal wavelength at 265nm is the most effective to kill harmful microorganisms via molecular lesions of DNA and RNA in the air, water and on surfaces as this is the absorption peak of DNA and RNA. Disinfection can occur more efficiently at different wavelengths via different disinfection mechanisms such as cell wall degradation which will cause death. Sometimes the optimum peak wavelength may not be the best choice of wavelength. If an alternative LED wavelength delivers higher intensity and dose at a more efficient cost, it may be a better choice that the “optimum wavelength”.

  Irradiance is a measure of how much UV energy falls on a particular surface point. Importantly, it is not the same as how strong a particular UV lamp is. A 10W lamp that emits UV in all directions, for example, may provide lower UV irradiance at a particular spot than a 5W lamp that focuses its UV output in a narrow beam.

  Time: The effective UV energy density, or dose, is the amount of UV energy that falls on a surface for a particular time. It refers to the necessary UV energy required for micro-organisms (bacteria, viruses, algae in suspension…) to absorb to the point of being neutered or killed.

• UV mercury lamps have been considered the best choice for disinfection and sterilization. Why is that?

  Historically, mercury lamps have been the only option for UV disinfection and sterilization. With advancements in UV LED technology, there are new options that are smaller, more robust, toxin-free, long lived, energy efficient and allow for infinite on/off switching. This allows solutions to be smaller, battery powered, portable and with instant full light output.

• What other technologies are currently in use?

  Mercury based UV lamps have a filling composed of mercury and a starting gas usually Argon. There are two major types differentiated by the mercury vapor pressure in the lamp. Low-pressure lamps emit at a wavelength of 253.7nm. High pressure lamps radiate a broad-band UVC radiation, rather than a single bandwidth. The issue with UVC Mercury lamps is their size, toxic mercury usage, and need for chlorine to enable effective disinfection.

  Excimer lamps produce UV light by spontaneous emission of Excimer molecules. Excimer lamps are mercury-free, instant on lamps which generate low levels of heat in comparison to mercury lamps. However, Excimer lamps have a low UVC efficiency and high cost. 

• What are the advantages of using LEDs for disinfection versus the other technologies identified?

  1. LEDs are environmentally friendly. They produce no Ozone.
  2. UV LEDs can be manufactured to operate at the optimum wavelength for the application: 265nm is widely recognized as the peak absorption of DNA; however, SETi has demonstrated that the peak disinfection efficacy of E.coli in water occurs at 275nm.
  3. Instant on/off and pulsing possible
  4. Compact form factor
  5. Low power consumption

• Does UV light damage food?

  No, in fact UV can be beneficial to food processing, production and help with maintaining freshness. Fresh food products are often processed using UV light to reduce the microbial load. Water has been treated with UV light to obtain drinking water for quite some time.

  Ref. Hinds LM, O’Donnell CP, Akhter M, Tiwari BK. Principles and mechanisms of ultraviolet light emitting diode technology for food industry applications. Innov Food Sci Emerg Technol. 2019;56(January):102153. doi:10.1016/j.ifset.2019.04.006

• Measuring disinfection

  The degree of disinfection is directly related to the UV Energy density (or dose) applied. The amount of UV Dose depends on the intensity of light and amount of time light is applied. There are actually six levels of disinfection or effectiveness. The levels are based on the reduction factor; see table. If log reduction is measured directly after exposure, colony numbers will be low. However, it is important to re-count colony numbers after a period of time to see if any organisms reproduce after exposure. The United States Environmental Protection Agency (USEPA) lays down guidelines that state the minimum log reduction for commercial disinfection systems

  Ref: Ultraviolet disinfection guidance manual for the final long term 2 enhanced surface water treatment rule, United States EPA, November 2006

   

  Log Reduction	Reduction	Number of Bacteria left from a colony of 1 million
  1	90%	100,000
  2	99%	10,000
  3	99.9%	1000
  4	99.99%	100
  5	99.999%	10
  6	99.9999%	1

  Table Log reduction

• What are the best wavelengths for UV disinfection?

  A wavelength of 265nm is considered the optimum as it is the peak of the DNA absorption curve. UVC has been shown to be effective in the disinfection of water, air, and surfaces on various pathogens such as E. coli, L. innocua, and COVID-19. However, disinfection and sterilisation occur over a range of wavelengths and in certain applications alternative wavelengths should not be dismissed. UVC LEDs can be manufactured to target very specific and narrow wavelengths. This allows solutions to be tailored to the particular application need. 

  Inside the semiconductor material of the LED, the electrons and holes are contained within energy bands. The separation of the bands determines the energy of the photons (light particles) that are emitted by the LED. The photon energy determines the wavelength of the emitted light, and hence its color. Different semiconductor materials with different bandgaps produce different colors of light. One the advantages of LEDs over Hg lamps is the precise wavelength (color) can be tuned by altering the composition of the light-emitting, or active, region. 

• How does UV-C Disinfection work?

  UV based Disinfection (often termed as Ultraviolet germicidal irradiation or UVGI) is the use of ultraviolet (UV) energy (electromagnetic radiation with a wavelength shorter than that of visible light) to kill or inactivate viral, bacterial, and fungal species. Different wavelengths of UV in the range of 200nm to 300nm are absorbed by DNA, RNA and proteins. When UV light is incident upon the target source the incident photons are absorbed by DNA or RNA and cause inactivation of the DNA or RNA double helix strands through the formation of molecular lesions. If enough of these lesions are created, the replication process is disrupted, and the cell cannot reproduce. Also, absorption by proteins can lead to the breakdown of organism’s cell walls causing the cell to die. For most applications, replication prevention is sufficient. The UV doses required to prevent replication are much lower than required to kill, making the cost of UV treatment to prevent infection commercially viable. 

• Is UV-C light harmful? / Are UVC LEDs safe?

  UVC lamps have been used for many decades to sanitize water, air and surfaces. However, precautions must be taken with this technology. Working unprotected for even a few minutes can cause injury.

  UVC light is invisible to the human eye so during operation the light can be mistaken for being benign causing eye damage. As negligible heat is produced by UVC LEDs the user may not realize the danger until after the exposure has caused damage to the skin. Symptoms typically occur 4 to 24 hours after exposure. More serious effects of UVC include accelerated skin aging and skin cancer. 

  Traditional UVC lamps shorter than 250nm produce ozone which is emitted into the environment and needs to have appropriate infrastructure to remove. Some UVC lamps are made using mercury so safe disposal is essential. UVC LEDs do not emit ozone or contain mercury. 

• Does Each LED emit only a single wavelength?

  No light source has a single wavelength. Light sources have a bandwidth. The wavelength used by LED manufacturers or LED Lamp manufacturers is based on the LED’s peak wavelength. This is the wavelength at which the source emits the most power. Ideally, all the light emitted from an LED would be at the peak wavelength, but in practice the light is emitted in a range of wavelengths centered at the peak wavelength. This range is called the spectral width of the source. The light output of a typical LED has a narrow spectral bandwidth from +/- 10nm to +/- 30nm. Reputable LED Lamp manufacturer’s datasheets will include this information.

• Are 220nm LEDs available?

  220nm LEDs are not commercially available right now. UV-C LEDs are a relatively new technology. The lowest wavelength available to buy is 255nm.  However, UVC LED technology is rapidly developing and overtime new wavelengths will be developed, costs will reduce and efficiencies will increase as has already happened within the visible, infrared, violet and UVA and B wavelength LED ranges. 

• What is UV light and the range of UV LEDs?

  Ultraviolet light (UV) is in the range of 200-395nm and are of three types: UVA, UV-B and UVC. UV-C is the UV range of 200-280nm. Typical UVC LEDs in the market emit at 255, 265, 270 and 285nms. While UV-A is now being used in curing applications effectively, UVC LEDs are now starting to be commercialised for applications cleaning, disinfection and sterilising applications.

• What are UV-C LEDs?

  A UVC light-emitting diode (LED) works like any other LED. It is a semiconductor device that emits light when an electric current is passed through it. Light is produced when the particles that carry the current (known as electrons and holes) combine together within the semiconductor material. Since light is generated within the solid semiconductor material, LEDs are described as solid-state devices. It distinguishes LEDs from other sources that use heated filaments (incandescent and tungsten halogen lamps) or gas discharge (mercury lamps).

  The UVC wavelength band is defined as being in the range 200-280nm. Currently LEDs are commercially available between 255nm to 280nm.