What is a Germicidal or UVGI
Germicidal or Ultraviolet Germicidal Irradiation (UVGI)
lamps are used to: disinfect air and water; cure inks
and coatings, disinfect foods and destroy pollutants
in water and air through UV-based "advanced oxidation".
UV energy can be effective in killing biological contaminants
such as mold/fungi, bacteria and viruses. For air disinfection,
lamps are typically placed inside air handling ducts,
mobile room air cleaning units and in special fixtures
mounted toward the ceiling in rooms. The most common
applications are in hospital / health care facilities,
food processing plants, shelters, prisons, and other
commercial uses where it is important to eliminate biological
contaminants. The target wavelength for most ozone-free
air purification applications is 254 nanometers. For
water purification, ozone producing wavelengths are
included and the target wavelength is 185 nanometers.
How does a Germicidal or UVGI Lamp Work?
Ultraviolet germicidal irradiation is produced by low-pressure
mercury lamps similar to fluorescent lamps without a
phosphor and with a quartz bulb. These lamps emit UV
in the 200nm to 300nm range or that portion of the UV
spectrum called UV-C. Also known as "shortwave" UV,
it includes the target germicidal wavelength of 254nm.
95% of the relative intensity occurs at the mercury
discharge line of 254 nanometers - proven to be the
most effective in germicidal applications.
More on UVGI.
Ultraviolet rays have shorter wavelengths
than visible light. A wavelength, the distance between
the crests of two waves, is often measured in units
called nanometers. A nanometer (nm) is a billionth of
a meter, or about 1/25,000,000 inch. Wavelengths of
visible light range from about 400 to 700 nm. Ultraviolet
wavelengths range from about 1 to 400 nm and are beyond
the range of visible light.
Ultraviolet technology is a non-chemical
approach to disinfection. In this method of disinfection,
nothing is added which makes this process simple, inexpensive
and requires very low maintenance. Ultraviolet purifiers
utilize germicidal lamps that are designed and calculated
to produce a certain dosage of ultraviolet (usually
at least 16,000 microwatt seconds per square centimeter
but many units actually have a much higher dosage.)
The principle of design is based on a product of time
and intensity - you must have a certain amount of both
for a successful design.
Ultra Violet irradiation is an effective
method of killing a broad range of microbes. In essence,
the UV radiation breaks the molecular bonds in the organism's
DNA. The most effective wavelength for accomplishing
this is 263nm; however, the very intense 254nm output
from low pressure Hg lamps is also very effective, as
well as broader spectral output from medium pressure
UV disinfects through a photochemical
process. The contaminants that pollute the indoor environment
are almost entirely based upon organic or carbon-based
compounds. These compounds breakdown when exposed to
high intensity UV at 240 to 280 nm. Short-wave ultraviolet
light can destroy DNA in living microorganisms and breakdown
organic material found in indoor air. UVC effectiveness
is directly related to intensity and exposure time.
Also see ultraviolet light definition.
Germicidal lamps emit UV which can be harmful. Caution
notices are provided in accordance with ANSI / IESNA
RP-27.3-96 Recommended Practice for Photobiological
Safety for Lamps - Risk Group Classification & Labeling.
Germicidal lamps are in Risk Group 3 (High Risk). Avoid
exposure to eyes and skin to unshielded lamp. Skin or
eye injury will result. Proper fixturing and operation
is essential for safe and effective application of this