The Germicidal Nature Of UV Light

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 400nm to about 1nm 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  - between 280nm and 200nm - is called the germicidal bandwidth. UVC has been used in hospitals for decades to disinfect the indoor air, surfaces and instruments in operating rooms. Many food and drug companies use UV fixtures with germicidal lamps to disinfect various types of products and their containers.

UV disinfection is a photochemical process. The microorganisms that pollute the indoor environment are DNA or RNA based. The cell membranes and DNA break down when exposed to high intensity UV at 253.7nm. This is the process through which short-wave ultraviolet light can disinfect liquids, surfaces and indoor air. The effectiveness of UVC is directly related to intensity and exposure time. Environmental factors like humidity, airborne mechanical particles and distance can also affect the performance of the UV fixtures.

The microorganisms must be exposed for a sufficient period of time to germicidal UV in order for the UV rays to penetrate the cellular membrane and breakdown the molecular bonds. This bond breakage translates into cellular membrane damage in which case the cells dye or DNA/RNA damage which renders the germs harmless because they can no longer  reproduce and cause diseases.

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