Germicidal lamp basics
UVC light
_UV is an abbreviation for Ultraviolet. It is a spectrum of light just
beyond the visible range. UV light is divided into four ranges of
wavelengths: (1) Vacuum UV from 100 to 200 nanometers, (2) UV-C from 200
to 280 nanometers, (3) UV-B from 280 to 315 nanometers, and (4) UV-A
from 315 to 400 nanometers. The UV-C spectrum (200 to 280 nanometers) is
shown to be the most lethal range of wavelengths for microorganisms, because it disrupts the
chemical bonds between the atoms which, in biological terms, results
in a “dead” microorganism. This range of wavelengths is also known as
the Germicidal Spectrum.
Inactivated DNA of microorganisms
_A low-pressure germicidal UVC lamp is made out of very clear quartz glass tube.
Inside each end of the tube there is a coil. When the lamp is turned
on, between these two coils an electric arc is created. This electric
arc has enough energy to vaporize a very small amount of mercury inside
the lamp which in this form emits a photon of light mainly with the
wavelength of 254 nanometers (nm). The 254nm light is known to destruct
microbial genetic material such as RNA (ribonucleic acid) and DNA
(deoxyribonucleic acid). The absorption of UVC light mainly occurs in
the nucleotide bases: adenine, guanine, cytosine and thymine, and uracil
in the case of RNA. The absorbed UVC light damages the DNA structure
by fusing two adjacent thymine molecules, producing thymine dimers. The
formation of these dimers prevents the DNA to replicate, hence
inactivating the whole microorganism.
Germicidal lamp
_
The
natural source of UVC light is the sun. It emits about 10% of its
energy in the UV region. However since it is mostly blocked by the
earth’s atmosphere it has no germicidal effect in our immediate
environment, like our home’s indoor air quality or our water systems. UV
Lamps are the other source of UVC light. UVC Lamps are commonly
referred to as Germicidal Lamps. There are two primary types of
Germicidal lamps, low-pressure lamps and medium pressure lamps. Low
pressure germicidal lamps produce 90% of their UV output at 253.7
nanometers (often referred as 254 nm) wavelength that is most effective
in inactivate microorganisms. The low-pressure lamps convert 35% of the
electrical power to UV energy vs. medium-pressure lamps that can only
convert 7% of their input power into useful UV energy the rest turns
into visible light and heat. Also Medium-pressure lamps have a peak UV
output at 365nm and secondary peaks at 334nm and 313nm wavelengths,
which work very effectively in surface curing applications. Depending on
the application and its design both lamps has its certain advantages
as a continuous UV light source.