Photobiological safety in lighting

Photobiological safety refers to the potential risk of photochemical damage to the eye caused by electromagnetic radiation from light sources, primarily in the wavelength range between 400 nm and 500 nm.

Legal framework

To assess the photobiological safety of optical radiation generated by lamps, measurement standards and benchmarks have been established, which are set out in the international standard IEC 62471:2006. This has been implemented in Europe as EN 62471:2008. It complies with European Directive 2006/25/EC.

Assessment of blue light hazard from light sources

For the assessment of the photobiological hazard, a distinction is made between different wavelength ranges: UV, visible and IR radiation. The decisive factor here is the depth of penetration into human tissue. UV radiation is already absorbed in the outer layers of skin tissue. The hazard and the specified limits depend on the illuminance generated; i.e. the risk increases with increasing proximity to the light source (regardless of size).

The situation is different for blue light hazard. This radiation penetrates through the cornea of the eye and impinges on the retina. Small sources with high luminance generate a high localised risk, whereas the identical radiant power from a broad source is spread out over a larger area and thus represents a lower risk.

Risk classification of lamps and luminaires

For all types of hazard, there are measuring methods as well as limit values of the radiance or irradiance, by which light fittings can be classified into risk groups (RG) from level 0 to 3.

In accordance with DIN EN 62471. The risk groups relate to a common reference distance of the eye from the light source. Since the luminance cannot be increased by lenses or reflectors, etc., the light source represents the greatest possible hazard, and the classification of the light source can be assumed for the luminaire.

From the classification under group RG2, light fittings must be labelled and marked with a warning that indicates the photobiological hazard and options for preventing eye damage. (See below)

Further details on blue light hazard can be found at: www.zvei.org/presse-medien/publikationen/fotobiologische-sicherheit-in-der-beleuchtung

If you have any questions about the specific values of blue light hazard for XAL luminaires or components, please contact: tech.lab@xal.com.