Ultraviolet (UV) is one energy region of the electromagnetic spectrum. It lies between the x-ray and visible region. UV itself lies in the ranges of 200 to 390 nanometers. Optimum UV germicidal action occurs at 260 nanometers.
Since natural germicidal UV from the sun is screened out by the earth’s atmosphere, we must look to alternative means of producing UV light. This is accomplished through the conversion of electrical energy in a low-pressure mercury vapor (hard glass) quartz lamp. Electrons flow through the ionized mercury vapor between the electrodes of the lamp, which then creates UV light.
As UV light penetrates through the cell wall and cytoplasmic membrane, it causes a molecular rearrangement of the microorganism’s DNA, which prevents it from reproducing. If the cell cannot reproduce, it is considered dead.