On May 7, 2020 IES hosted a 3.5 hour webinar on UV Germicidal Lighting. The purpose of this page is to share and highlight some important information. As a lighting designer, I am sharing some of what I have learned,  I am not giving medical advice, please consult your doctor.

UV Lighting for COVID-19 - Learning Objectives

  1. UV Germicidal Light History 
  2. Ultraviolet Wavelengths
  3. UV Types of Disinfection
  4. UV Dose & Terminology
  5. UV Safety
  6. UV Light Sources
  7. UV Lighting Installation & Maintenance​
  8. ​UV Paint
  9. Best online UV Germicidal Light Resources

History of Germicidal UV Light

1877 - Discovery of the ability of sunlight to prevent microbial growth. Dose = intensity + time combined with the wavelength expressed in nm and the sensitivity of the organism.
1930’s - Upper room air disinfection with measles.
1946 - Applications of Germicidal, Erythemal and Infrared Energy, Book by Matthew Luckiesh
1960’s - TB (Tuberculosis) research introduces mixing the upper room UVGI irradiated air with the lower room air.
1990's to present - Resurgence of TB encouraged more upper-room UVGI research to prevent TB transmission.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2789813/
​2009 - Upper-Room Ultaviolet Light and Negative Air Ionization to Prevent Tuberculosis Transmission -  https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1000043
Ultraviolet portion of Electromagnetic Spectrum
Ultraviolet portion of Electromagnetic Spectrum

Ultraviolet Wavelengths

Radiation type
  • Wavelength Infrared radiation (IR) 42–45% of solar spectrum 760 nm – 1 mm
     IRA (near*) 760–1400 nm
     IRB (mid or middle) 1400–3000 nm
     IRC (far or long) 3000 nm – 1 mm
  • Visible Light 380 - 740 nm  Visible (light) 50–52% of solar spectrum 380–780 nm
     Red 625–780 nm
     Orange 590–625 nm
     Yellow 565–590 nm
     Green 500–565 nm
     Blue 435–500 nm
     Violet 380–435 nm - Efficacy of violet light, 405 nm, effective in specialized organisms, can re-activate some DNA. 
    https://strathprints.strath.ac.uk/48883/1/DOI_10.1016_j.jhin.2014.06.004_accepted_manuscript.pdf
  • Ultraviolet - UV 5–6% of solar spectrum 100–400 nm
     UV-A 315–400 nm Blacklight
     UV-A1 340–400 nm
     UV-A2 320–340 nm
     UV-B 280–315 nm Sunburn (​Erythema) 300 nm UVB - Skin Cancer (CIE) 
     UV-C 100–280 nm315 nm - 400 nm UV-A
  • The UV-C part of the UV spectrum has the highest energy. Whilst it is possible to damage some microorganisms and viruses with most of the ultraviolet radiation spectrum, UV-C is the most effective and hence UV-C is most commonly used as GUV.  250 nm reduced biological effect, although can be skin cancer from repeated exposure.
  • 270 nm - Germicidal action peak
  • 254 nm - Room must be vacant, unless it is 'upper room' UV-C and not directed into eyes hor highly reflective surfaces.  
  • 222 nm - possible skin damage, await clinical trial
  • 207 - 222 nm - Far UV-C germicidal light = 0 occcupancy
  • Below 200 nm create ozone
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3834711/
GUV wavelengths ChromaTherapyLight.com
Double Click to Enlarge Image

Types of UV Disinfection

  1. Indirect - with occupants - upper room air disinfected and mixed with Lower room air.​ Use  Commissioning CAD UVGI Tool to evaluate unintended reflections with sloping ceilings.
  2. Direct - without occupants, also for respirator chambers.
  3. Pulsed Light - without occupants.
  4. HVAC - UV-C does NOT remove viral, fungal, or bacterial particles; rather, it inactivates them. Slowest moving air in HVAC system is preferred; air speed, temperature and line depth have effects. 
  • Air filter entry - before particulate filter.
  • Air Filter - during particulate filter to clean filter, not the air necessarily.
  • Air filter exit - after particulate filter, air moves quickly, difficult to achieve long exposure.
  • Combination systems - Lamps in warmer air on the entering side for increase infection control plus lamps on leaving side for coil and drain pan maintenance.​
  • Portable units, room air cleaners, require regular maintenance and will have zones of no treatment due to physical barriers and furniture.
  • Hand held devices can be extremely dangerous to the eyes and without considerable dosing time, ineffective.
Upper Air Germicidal Ultraviolet Installation
Upper Air Germicidal Ultraviolet Installation - requires air mixing.

Ultraviolet Dosing Terminology

2009 GUV Dosing Criteria CDC Guidelines - https://www.cdc.gov/niosh/docs/2009-105/pdfs/2009-105.pdf
Dose = intensity + time combined with the wavelength expressed in nm and the sensitivity of the organism.
Wavelength = A typical human eye will respond to wavelengths from about 380 to 740 nanometers called the visible spectrum or simply light.
Ultraviolet light is electromagnetic radiation with wavelength from 10 nm to 400 nm
nm = nanometer is the term used to describe the wavelength of a color or part of the electromagnetic spectrum. (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (0.000000001 m). 
Watt - Output power of given lamp expressed in watts, not using Lux or Lumens as in visible light. Lamp radian output to effective dose rate. Lamp radian output to effective dose rate.
Duration - Exposure time.
Intensity - UV-C Irradiance measured in watts.
Air Exchange = CFM - Cubic Feet per Minute
Air, surface, or moisture require different methods.
CADR - Clean Air Delivery Rate (HVAC actual airflow rate corrected for particle removal efficiency)
ACH - Air Changes per Hour (HVAC)
Lamp - Light bulb
Luminaire - Housing, lamp, transformer or ballast, wiring assembly combined to make a complete light fixture.

UV
Germicidal
Light
Safety
​Concerns
Human eyes are sensitive to UV light, risking blindness.
Human eyes are sensitive to UV light, risking blindness.
  1. UV-C products present risk, should be used by professionals who must shield their eyes and skin to avoid light damage and severe injuries to the eyes and skin.
  2. Human access and duration of exposure are factors.
  3. Transient photo = eye injury. The Cornea tissue of your eye is susceptible to UV burning, feels like sand in your eyes, or complete blindness. Photokeratitis, welder's flash, snow blindness have a delayed response and will not be immediately evident. Blindness may occur as a result of UV light exposure, it can damage your eye's retina. 
  4. Repeated exposure may cause skin reddening and possibly skin cancer.
  5. UV will degrade materials over time, furniture and plastic covered upholstery, and medical equipment. Sanitizing face masks with UV will make elastic fail the first day.
  6. Blue light does not mean Germicidal.

Ultraviolet Light Sources

  • Low pressure mercury lamp, patent in 1886, long before fluorescent.
  • Bluish green glow is visible mercury lines, two in blue one in green.  you cannot see the germicidal wavelenghts; however, seeing the blue green light enables you to see the cutoff of the beam of Upper Room UVGI.
  • Fluorescent without phosphor is germicidal lamp,  phosphors convert UVC to visible light.
  • LED - lower than 254 nm is difficult with LED. Efficiency very low at this time. 270-280 right next to UVB, skin and eye damage much higher. Safety concern even more so than high pressure mercury.
  • Halogen Quartz - 
  • Mercury Vapor -
  • Krypton lamps not proven to protect skin and eyes.
  • Mercury-Free Far UV-C Excimer Lamps​ -222nm with visible tail, visible region looks like mercury lamp. (allows you to see cut off of radiation emissions)

Installation & Maintenance

  • Over time, output decreases affecting disinfection. Light loss due to dirt depreciation and aging lamps require regular testing and maintenance. 
  • Electricians - “do not look at UV light.” Be sure the interrupter circuit is in place before maintenance.  Access interlock switches required on HVAC systems.​
  • Plastic lens - none of UV-C goes through plastic, making the fixture useless.
  • Poor installation - upside down fixtures can cause eye injury.
  • Poor fixture design, high ceiling fixture mounted on low ceiling allows for eyes to see damaging UV light.
  • Portable units, room air cleaners, require regular maintenance and will have zones of no treatment due to physical barriers and furniture.
  • Soap and water left uniform residue on lamp decreasing , performance went up with a second alcohol cleaning.
  • UV lamps (UVC254) are not the same as less expensive 'blue fluorescent' lamps, exact match of replacement lamp required.
  • HVAC, electrical, furniture, and other equipment degraded by UV-C.​​

Reflectance for UV is different than Visible Light

UV 254 Reflectance from different materials
Reflectance for UVGI - ARTI-21 CR-160-40030-01
Defining the use of UV effectiveness in circulating air ductworks 2002
https://www.osti.gov/servlets/purl/810964
UV 254 nm Reflectance from different materials - How is  UV reflection different from Visible Light reflection? "Many surfaces reflect UV radiation and add to the overall UV levels you experience. While grass, soil or water reflect less than 10 per cent of incident UV radiation, sand reflects about 15 per cent, and sea foam about 25 per cent. Fresh snow is a particularly good reflector and almost doubles a person's UV exposure. Recurring incidences of snow blindness or photokeratitis in skiers emphasize that UV protective measures must take ground reflection into account." World Health Organization
https://www.who.int/news-room/q-a-detail/ultraviolet-(uv)-radiation
And
https://www.ccohs.ca/oshanswers/phys_agents/ultravioletradiation.html

UV Paint Finishes

An example, Sherwin Williams recommends Utilize Saniglaze wall system with the GP4410 flat urethane finish. The 4410 will be the most resistant to high UV scenarios and still hold its color and gloss.
Utilize warm colors with lower light reflectance values. Warmer colors will absorb fugitive UV where as lighter colors will reflect the UV off of its surface. [PDM, Protective Coatings Division, Sherwin-Williams Co.]

With all paints, the LRV (Light Reflectance Value) decreases as the colors become darker. Industrial Safety Colors, and Finish options and Chemical Resistance links below.
SW LRV (Light Reflectance Value) - I & M Color Chart 2003
SW Safety Colors - Corothane 2003
SW Aquarmor WBU - Water Based Urethane (Two Part)
SW Saniglaze
SW Chemical Resistance Guide 2002
LRV - Light Reflectance Example - SW LRV (Light Reflectance Value) - I & M Color Chart 2003
LRV - Light Reflectance

UV Germicidal Lighting Companies

Visible Light Disinfection

​See Lighting for Healthcare page for more information.

Lighting for Hospitals and Healthcare Facilities | IES

https://www.ies.org/product/lighting-for-hospitals-and-healthcare-facilities/
WHO Guidelines on tuberculosis infection prevention and control
WHO Guidelines on tuberculosis infection prevention and control

Best online UV Germicidal Light resources - ask the experts

Footnotes

  1. Citations in this page are shown as links at the end of the paragraph for quick reference.

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