Disinfection lights and germicidal lamps produce ultraviolet (UV) radiation that can activate destructive photochemical reactions and ultimately lead to inactivation of bacteria and viruses. UV is a form of electromagnetic radiation with a wavelength shorter than the visible rays and longer than the X-rays, ranging from 100 to 400 nanometers. The electromagnetic spectrum of ultraviolet radiation can be subdivided into a number of ranges, including UV-A (long-wave) from 315 to 400 nm, UV-B (medium-wave) from 280 to 315 nm, and UV-C (short-wave) from 100 to 280 nm. UV radiation in wavelengths of 100 – 200 nm is commonly called vacuum UV as the photons are absorbed in the ionosphere and by atmospheric oxygen. While UV-C light from 100 to 280 nm is viricidal, bactericidal and fungicidal, the range of UV of particular effectiveness and usability for disinfection and sterilization lies in the spectral band from approximately 200 to 280 nm. Common sources of UV-C in commercial applications are generally engineered to deliver a peak emission wavelength within this band.
Disinfection lights and germicidal lamps are used for air, surface, object and water disinfection in industrial, commercial, medical, public and residential environments. Germicidal UV (GUV) radiation sees its increasing applications in in enclosed spaces where trapped or recirculated indoor air may contain microorganisms and viruses. These contaminants and the associated airborne infections can be considerably reduced by installing lights near coils and drain pans of air conditioning systems or in the upper part of a room, where it does not reach people directly, to destroy floating particles in the air. Ultraviolet germicidal irradiation (UVGI) systems are used to disinfect the upper air layers within rooms. Through the mechanism of natural or forced air convection, air flows from the lower areas of a room where people are circulated to the upper areas of a room and get disinfected as they pass through the UV-C disinfection zone. Air disinfection with open UV-C fixtures that radiate UV-C directly without shielding are mostly used in spaces where access of occupants is controlled.