PHOTOBIOLOGICAL SAFETY :
In solid state lighting products such as LEDs, LED modules, LED lighting fixtures, etc., the photobiological safety standard must be necessarily applied against the damage of light to the eyes and skin and the blue-light hazard.
Wavelength spectrum of fixtures emitting white light at different CCT values is given in Figure 1. When the wavelength spectrum of lighting fixtures (those with white light and / or narrow band radiation) is examined, it is observed that the fixtures can emit a small amount of pre-violet and/or infrared radiation. It is known that the light radiating in the given area leads to damage to the eye (on the cornea/retina) and skin. The LEDS used in lighting fixtures must be certified according to the standards that they do no cause damage to the eye and skin layer in photobiological terms. According to EN 62471 which is the relevant standard of the European Union, the products radiating between 200nm and 3000nm should be subject to the tests within the scope of this standard.
Figure 1. Wavelength spectrum of LEDs radiating typical White light at different CCT values
RISK CLASSES
According to EN 62471: 2008 Paragraph 6.1, the risk groups (for blue-light) are defined as below:
- Risk Group 0 (Exceptional Group): It does not lead to any photobiological hazard.
- Risk Group 1 (Low Risk): The fundamental philosophy for this classification is that the lamp does not present any hazard due to the normal behavioral limitations in exposure.
- Risk Group 2 (Medium Risk): The fundamental philosophy for this classification is that the lamp does not present any hazard due to the risk aversion response to very bright light sources or thermal distortion.
- Risk Group 3 (High Risk): The fundamental philosophy for this classification is that the lamp may present a regular hazard for sudden or short exposure.
Figure 2. Risk groups and exposure time
Risk groups and maximum exposure time to light according to these groups are given in Figure 2.
Exposure time for risk group RG0 is approximately 10000 seconds (~3 hours). It may pose a risk only when looking at a fixture continuously and directly for longer than that.
Maximum exposure time to RG1 armatures is 100 seconds. Exposure to a direct light source for less than 100 seconds under ordinary conditions of use is not considered hazardous.
In case risk group RG1 limits are exceeded, it is accepted as risk group RG2. The radiation limits specified in the standard for risk groups are given in Table 1. Maximum exposure time for RG2 class is 0.25 second. The products under this risk group is considerably bright. Therefore, sudden closure and blinking of the eye as a reflex is observed. It does not cause any damage on the retina when looking directly at the light for less than 0.25 second.
| Risk Group | Radiation and exposure time limits | ||
| RG 0 | 10000 sn | 100 W/(m2sr) | 1 W/m2 |
| RG 1 | 100 sn | 100000 W/(m2sr) | 1 W/m2 |
| RG 2 | 0.25 sn | 4×106 W/(m2sr) | 400 W/m2 |
When performing lighting design, the use of lighting products and lighting fixtures that comply with the relevant safety and performance standards should be taken as basis.
The current EN 60598-1 standard concerning general lighting fixtures show that RG0 or RG1 risk groups are acceptable for safety purposes. It is not suitable to use light sources with a higher degree than RG2. There is no need to mark the fixtures with risk group RG0 or RG1. When RG2 limit condition 2 is reached, the limit distance must be calculated according to IEC/TR 62778 (see article 5 of this document). If the distance is higher than 20 cm, the requirements below are recommended:
- In case of a fixed lighting fixture, the manufacturer instruction sheet will give the advice below for the assembly: “The fixture should be placed in such a way that it is not expected to be viewed for a long time at a distance closer than X m to the fixture.” (X m is the distance between light source and the eye or the audience). Additionally, if the light source is directly visible during maintenance, the lighting fixture will be provided with the symbol below.
- The following symbol will be required for portable and hand-held fixtures.
Do not look directly at the operating light source.