UV light is electromagnetic radiation with wavelengths shorter than visible light. UV can be separated into various ranges, with short-wavelength UV (UVC) considered "germicidal UV". At certain wavelengths, UV is mutagenic to bacteria, viruses and other microorganisms. Particularly at wavelengths around 250 nm to 260 nm, UV breaks molecular bonds within DNA, producing thymine dimers that can kill or disable the organisms. It is a process similar to the effect of longer wavelengths (UVB) producing sunburn in humans. Microorganisms have less protection from UV and cannot survive prolonged exposure to it.
There are several types of ultraviolet disinfection equipment:
- Upper air ultraviolet radiation disinfection
Mostly it will be used in the operating room, passageways, corridors, persistent exposure. In order to avoid harming human eyes and skin, it should be installed in ground 2 to 2.5 meters height. The irradiation range is upper space of the operating room, through the cold air drops, the hot air rising convection cycle, continuously reducing the number of microorganisms in the operating room
- Water sterilization
Ultraviolet disinfection of water is a purely physical, chemical-free process. Even parasites such as cryptosporidia or giardia, which are extremely resistant to chemical disinfectants, are efficiently reduced. UV can also be used to remove chlorine and chloramine species from water; this process is called photolysis, and requires a higher dose than normal disinfection.
- Air disinfection
UVGI can be used to disinfect air with prolonged exposure. Disinfection is a function of UV intensity and time. For this reason, it is not as effective on moving air, when the lamp is perpendicular to the flow, as exposure times are dramatically reduced.