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 rays with wavelengths shorter than 300 nm are extremely
effective in killing microorganisms. The most effective sterilizing
range for UV is within the C bandwidth (UVC). This range is called
the germicidal bandwidth. UVC has been used in hospitals for decades
to sterilize surgical instruments, water, and the air in operating
rooms. Many food and drug companies use germicidal lamps to
disinfect various types of products and their containers.
The cleansing mechanism of UV is 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’s effectiveness is directly related to intensity and exposure
UV rays must strike the contaminants directly in order to penetrate
the microorganism and breakdown its molecular bonds. This bond
breakage translates into cellular or genetic damage with the germs
rendered harmless by robbing them of the ability to reproduce.