Effect of UVC disinfection
Invisible optical radiation, how can it be disinfecting?
UVC as part of the light spectrum
Ultraviolet light or ultraviolet radiation is part of the light spectrum and has a shorter wavelength than visible light. Other invisible parts of the light spectrum include infrared and X-rays.
UV light is divided into UVA, UVB, and UVC. UVC light has a wavelength of 100 to 300 nm, but the 240-280 nm range is particularly is well absorbed by microorganisms.
The energy of the UVC light disrupts DNA and prevents microorganisms from multiplying. Professional disinfection bulbs mainly produce UVC light with a wavelength of 254 nm, which has the most powerful disinfecting effect.
UVC damages the DNA of microorganisms and viruses, which keeps them from multiplying.
A photo-chemical effect is created in the cell that causes dimming. Adjoining Cytosine and Thymine molecules bind to each other instead of to the opposite base in the DNA molecule.
That renders the DNA information useless, and the cell dies and can no longer divide. The effectiveness of UVC light has been extensively researched and published by scientists worldwide, the best known being Wladyslaw Kowalski.
The relationship between dosage and result
For many microorganisms, we know what dosage is necessary for critical damage. We call the dosage needed to deactivate 90% of the population the D90 dose.
Sensitivity to UVC light varies widely between different types of microorganisms. Viruses and bacteria are very sensitive, while yeasts and moulds are much more resistant to UVC light.
In practice, that means that moulds need a longer exposure time or a more powerful UVC bulb.
What are the risks?
UVC is invisible, but UVC bulbs emit a blue light as a by-product that has no disinfecting effect. It serves a practical function, letting you know that the bulb is switched on.
UVC radiation is dangerous to skin and eyes, so it's best to avoid exposure. All installations should be shielded and proper protective equipment such as a face masks and skin covering should be used during testing and maintenance.
Effect on skin:
Because UVC does not have an infrared component like sunlight, you won't feel its effects, but it can cause redness and a burning sensation on the skin fairly quickly.
Effect on the eyes:
UVC does not penetrate into the eye, but corneal irritation can occur a few hours after exposure. It causes a painful, burning sensation that's also known as "welder's eye" or "snow blindness".