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About UV Light

UV light (ultraviolet light), also referred to as ultraviolet radiation and UV radiation is invisible to the human eye. It occurs naturally in sunlight and is produced artificially, normally by either heating a body to an incandescent temperature or by excitation of a gas discharge.

UV light wavelengths are measured in nanometers (nm), where 1 nm = 1 millionth of a millimetre. It occupies a portion of the electromagnetic radiation spectrum which lies between x-rays and the blue end of visible light. This is the region from 100 nm to 400 nm.

The International Commission on Illumination (CIE 1970) has defined the following spectral range classification bands, according to broad biological effects. The region 315 nm to 380 nm or 400 nm is designated as UV-A, 280 nm to 315 nm as UV-B and 100 nm to 280 nm as UV-C.

UV light classification band




315nm - 400nm

280nm - 315nm

100nm - 280nm

Longwave or blacklight

Middlewave or erythemal

Shortwave or germicidal

Least potential to cause adverse health effects due to the lowest energy. UV-A represents the largest UV component of sunlight, (approximately 90 %). 

Greater potential to cause adverse health effects than UV-A due to significantly higher energy. UV-B is partially absorbed by the ozone layer. It is the most aggressive component of sunlight and largely responsible for sunburn (erythema). 

Generally, the most potential to cause adverse health effects due to the highest energy. Only normally encountered from artificial UV light sources, since it is totally absorbed by the earth's atmosphere. UV-C sources, particularly wavelengths less than 220 nm, in the presence of oxygen will produce ozone. 

Spectral Range

Common description

Potential to cause adverse health effects

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