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Frequently Asked Questions
No. We are building a complete system that combines expertise in materials, optics, GUV sources and biology to develop complete solutions.
Germicidal ultraviolet (GUV) – refers to short-wavelength ultraviolet radiant energy that has been shown to kill bacteria and to inactivate viruses. Wavelengths in the ultraviolet band known as the “UV-C” (from 200 to 280nm), have been shown to be the most effective for disinfection.
On a microscopic level, individual, UV-C photons interact with the RNA and DNA molecules in viruses and bacteria to render them non-infectious.
Germicidal effectiveness is proportional to the exposure dose (radiant exposure, typically in millijoules* per square centimeter, mJ/cm2, or joules per square meter, J/m2), which is the product of the radiant power (irradiance, typically in mW/cm2 or W/m2) and time (from 1 μs to several hours).
Germicidal effectiveness is usually measured on a log-scale, which is linearly associated with dose. For instance, if 1 mJ/cm2 UVGI (Ultraviolet germicidal Irradiance) achieves a 1-log (10-fold) killing rate, then 4 mJ/cm2 would achieve a 4-log (10,000-fold) killing rate. The 4-log rate is commonly referred to as 99.99%.
If a certain UV exposure kills 90% of a bacterial population (frequently referred to as "one-log kill"), doubling the exposure time or intensity can kill only 90% of the residual 10%, for an overall germicidal efficacy of 99% ("two-log kill"). To be effective in practice, achieving two log-kills (99% inactivation) is frequently accepted.
All known micro-organism is susceptible to UV-C. Bacteria, mold and fungi will be killed, and viruses will be inactivated. It is only a matter of how much time and how much radiant power is provided.
(Source: 1 Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae Revised, updated and expanded by Adel Haji)
The dose required to achieve 1-log killing is often called the D90-value (where 90% of the pathogen is killed), and these values have been empirically determined for many pathogens and microorganisms.
(Source: Kowalski -2017)
UVC has been demonstrated to work very effectively to inactivate viruses including coronaviruses.
(Source: Darnell et al. – 2004 showed that UVC exposure resulted in >5 log reduction of SARS-CoV.)
The National Emerging Infectious Diseases Lab at Boston University conducted research to confirm the effectiveness of Signify’s UV-C sources in inactivating SARS-CoV-2, the virus that causes Covid-19. The research team identified that a dose of 22mJ/cm2 will result in a reduction of 99.99% of SARS-CoV-2.
(Source: Signify Press Release)
No. GUV is a segment of UV-C electromagnetic wavelengths, while Near-UV is 405nm wavelength visible light.
While GUV has proven to be highly effective at inactivating viruses and other pathogens, Near-UV has limited effectiveness against viruses, and requires long exposure times to be effective on surface bacteria.
GUV poses a health hazard to the eyes and skin if the lamps are improperly used or installed.
We have developed a UL 1598 Safety Certified GUV System designed to meet new UL 1598 standards.
There are both low-pressure discharge “pin-based” and LED solutions available.
The LED solutions, however, are limited, and the efficiency is orders of magnitude lower than GUV.
The CLS solution will use bi-pin sources and specialized materials to maximize the power distribution of the GUV. While they look like lamps, they do not produce visible light, so they are considered to be emitters.
Similiar to light energy, we have tested IES files that provide the irradiance and the electrical power needed to operate each fixture.
Similiar to lighting layouts, we can translate this into power delivered to an area in the same manner we calculate foot candles.
The power can be translated to the time needed to eliminate a pathogen based on its “dose”. This time is typically planned for elimination of 99.99% from the surfaces. In many cases the “4-log kill” is accomplished in minutes.
Darnell, Miriam E.r., et al. “Inactivation of the Coronavirus That Induces Severe Acute Respiratory Syndrome, SARS-CoV.” Journal of Virological Methods, vol. 121, no. 1, 2004, pp. 85–91., doi:10.1016/j.jviromet.2004.06.006.
IES Committee Report
Germicidal Ultraviolet (GUV) – Frequently Asked Questions
The report was prepared by the IES Photobiology Committee with the goal of providing objective and current information on germicidal ultraviolet irradiation as a means of disinfecting air and surfaces. IES does not endorse or recommend any products.