Ultraviolet (UV) is that part of electromagnetic light bounded by the lower wavelength extreme of the visible spectrum and the X-ray radiation band. The spectral range of UV light is, by definition between 100 and 400 nm (1 nm=10-9m) and is invisible to human eyes.
UVA (long-wave) from 315 to 400 nm
UVB (medium-wave) from 280 to 315 nm
UVC (short-wave) from 100 to 280 nm
The germicidal range of UV is within the 100-280 nm wavelengths, known as UV-C, with the peak wavelength for germicidal activity being 265 nm. This range of UV light is absorbed by the DNA and RNA of microorganisms, which causes changes in the DNA and RNA structure, rendering the microorganisms incapable of replicating. Commercial bulbs produce UVC light at 253.7 nm.
UV light operates in a “line-of-sight” fashion, only irradiating surfaces within its sight-lines. In other words, it only is sanitizing where the light shines. UVC light also sanitizes airborne viruses and bacteria. So any Covid floating around in the air will be sanitized when the light is turned on.
Distance plays a factor into the efficacy of UV light. The strength of the UV-C light decreases the further away it gets from the light source, following the inverse square law. This means that at twice the distance from the source, the UV-C light will have 1/4 of its power that was present at the original reference point and at 3 times the distance the UV-C light will have 1/9 of its power.
The degree of inactivation of microorganisms by ultraviolet radiation is directly related to the UV dose applied.
Dose is the product of UV intensity (mW/cm²) multiplied by exposure time in seconds
This dose is expressed as millijoule per square centimeter (mJ/cm²).
There have been many studies over the last 50 years as shown in this document showing how much UVC dose in mJ/cm² is needed to reduce microorganisms. This is commonly expressed in logarithmic reduction.
A 1 log reduction, reduces a microorganism by 90%.
A 2 log reduction by 99%, a 3 log reduction 99.9% etc.
Specifically for SARS-CoV-2, I have referenced two 2020 studies that show the dose of UVC light needed to reduce SARS-CoV-2 by at least 99.9999%.
The Bianco Study shows a 6 log reduction (99.9999%)SARS-CoV-2 with 16.9 mJ/cm² of UVC radiation.
This Journal of Infectious Diseases article shows SARS-CoV-2 is reduced by 6 log (99.9999 %) with 40 mJ/cm² of UVC radiation.
Bulb manufacturers have specifications on the UVC intensity of their bulbs as shown in this Philips brochure.
BrightBot has verified these specifications by using a Certified UVC light meter to measure the UVC intensity of each light at specified distances to calculate how much time is needed to sanitize a room of a given size.
These products are meant to be used in unoccupied spaces.
Personnel should avoid exposure to UVC. Direct exposure to UVC light can cause erythema (reddening of the skin) and conjunctivitis (inflammation of the mucous membranes of the eye. Fortunately avoiding UVC light is relatively simple, because UVC is absorbed by most products, and even standard flat glass absorbs all UVC. Also, UVC is mostly absorbed by dead skin, so erythema can be limited. In addition, UVC does not penetrate to the eye’s lens. The permissible 254 nm UV exposures, per person/day is 6000uJ/cm² per ACGIH documented in this Philips UVC brochure
The BrightBot system is designed with a remote control so you can put the UVC light in a room, shut the door, exit the room and then turn the light on. During normal operation you should never be exposed to the UVC light according to the Phillips website.
Ozone is harmful to humans.
Ozone is produced at a wavelength of 185 nm.
Unlike cheaper bulbs used in other UVC disinfection systems, these bulbs have a filter in their glass that filters out the 185nm UVC light.
BrightBot has confirmed no ozone is produced using a Honeywell BW solo ozone meter.
The BrightBot system is simple.
Watch a demonstration video here.
Here are the steps:
The BrightBot UVC systems have a warranty of one year that covers defective components.
The warranty does not cover accidental bulb breakage or misuse.
The BrightBot UVC lights are built using a simple design with only the necessary components needed for their function of sanitizing rooms.
The remote control battery which is a few dollars may need to be replaced once per year. The bulbs are rated for 8,000 hours of use.
We recommend replacing the bulbs every year. If the bulbs get dirty or dusty, wipe with clean cotton cloth and alcohol.
Do not used bleach based wipes to clean the aluminum frames.
The BrightBot UVC line of UVC disinfection lights are made of industrial grade aluminum. Large 3 inch casters are used to roll the unit around.
They come with a heavy duty cover that should be used when the lights are not in use to protect the bulbs from breakage.
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Prolonged, direct exposure to UVC light can cause temporary skin redness and eye irritation.
Never use BrightBot products in rooms occupied by humans or animals.