Germicidial Lamp Basics
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.
