How Germicidal UV Lamps Work
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What Is Ultraviolet Light?
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Invisible to the human eye, ultraviolet (UV) light is a type of electromagnetic radiation whose wavelength is between 10 nanometers and 400 nanometers in length. With a range of wavelengths shorter than visible light's yet longer than x-ray's, UV light is considered "ionizing radiation," carrying a level of energy capable of doing serious damage to DNA molecules. UV light falls into three subtypes: UV-A (400nm to 320nm), UV-B (320nm to 280nm) and UV-C or "germicidal" (280nm to 100nm).
Types Of UV-C Germicidal Lamps
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UV-C lamps are filled with mercury vapor that, when excited by electricity, emit UV radiation between 254nm and 185 nm. Depending on the pressure of the mercury inside, a UV lamp will emit a very specific wavelength of light. The "low pressure" UV lamps emit a greater amount of 254nm light but at a lower intensity. Meanwhile, the "medium pressure" lamps emit less 254nm photons but with a stronger intensity. Given the impact distance has on effectiveness, low pressure germicidal lamps must be placed strategically while medium pressure lamps need longer exposure times.
How UV-C Radiation Destroys Viruses, Bacteria, Mold & Spores
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All organisms rely on their cellular DNA as a blueprint to direct their critical physiological activities, including reproduction. When UV-C light strikes the DNA nucleotide known as "thymine," its carbon-carbon double bond breaks, ruining the nucleotide's ability to pair with adenine. This inability to pair with its complementary nucleotide makes it impossible for the DNA to properly replicate and reproduce, rendering the organism sterile. This destruction of thymine also interferes with the cell's ability to translate that gene into critical, life-sustaining proteins.
Finally, if two thymines are next to each other in the DNA, UV-C destruction of both molecules will actually cause the nucleotides to fuse to one another. This leads to "kinking" in the structure of the helix, which weakens the molecular integrity around the site and makes the sequence more vulnerable to mutation.
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