ultravioletC

Ultraviolet C, or UV-C, refers to the portion of the ultraviolet spectrum with wavelengths roughly from 100 to 280 nanometers. UV-C is the shortest-wavelength UV band and is highly energetic, capable of damaging nucleic acids and proteins. This damage can inactivate microorganisms by preventing replication and transcription.

Natural UV-C from the sun is almost entirely absorbed by the Earth's ozone layer and atmospheric oxygen, so little reaches the surface under normal conditions. Consequently, terrestrial exposure to UV-C is typically from artificial sources rather than sunlight.

Artificial UV-C sources include low-pressure mercury lamps that emit a strong line near 254 nanometers and UV-C light-emitting diodes that cover about 260 to 280 nanometers. UV-C is widely used for disinfection and sterilization, including water treatment, air handling, surface decontamination, and sterilization processes in healthcare, food processing, and laboratories.

Infection control and hygiene applications rely on the germicidal properties of UV-C. Proper dosing—defined as fluence, the product of irradiance and exposure time, measured in millijoules per square centimeter—achieves microbial inactivation with varying effectiveness depending on organism, medium, and turbidity. UV-C is particularly effective against bacteria and viruses, though spores and some protozoa may require higher doses.

Safety, limitations, and maintenance are important considerations. Direct exposure to UV-C can cause skin burns and eye injuries; devices are designed with shielding, interlocks, and safety procedures to prevent accidental exposure. UV-C radiation can degrade plastics and other materials, and certain short-wavelength sources can generate ozone. Effectiveness can be reduced by water turbidity, organic matter, and shadowing, necessitating validated dosing and system design.