Eye safety is a complex topic. This article provides an overview of risk group assessments for a wide range of LED types. There are many active standards, and the user is advised to use the standard(s) that conform to local regulation. The list below summarizes the most commonly used standards.
- CEI/IEC 62471:2006 “Photobiological safety of lamps and lamp systems”
This standard defines risk groups and test methods developed to replace the older IEC 60825 laser standard with a standard specific to incoherent light sources. Most of the world uses this standard. - IEC/EN 62471:2008 “Photobiological safety of lamps and lamp systems (IEC 62471:2006, modified)”
This is a European standard that revises the 2006 standard to conform with the exposure limits in the Artificial Optical Radiation Directive (2006/25/EC). The risk group definitions in this standard are more conservative than those in IEC 62471:2006. EU countries use this standard. - IEC/TR 62471-2 “Photobiological safety of lamps and lamp systems – Part 2: Guidance on manufacturing requirements relating to non-laser optical radiation safety”
This technical report is an addendum to IEC 62471:2006 which gives guidance for lamps or lamp systems being assigned to a particular risk group and gives examples of labeling suggestions and application specific safety calculations. - IEC TR 62778:2014 “Application of IEC 62471 for the assessment of blue light hazard to light sources and luminaires”
This technical report addresses issues related to assigning risk groups to “GLS” white light sources and provides an alternate methodology to report white light risk assessments. This technical report also provides better guidance on the transferability of risk group levels from the component test to the luminaire. The “RG0 – unlimited” and “RG1 – unlimited” ratings are used to explicitly designate component test results that can be transferred to the luminaire without any further tests. - IEC 62031:2018 “LED modules for general lighting – Safety specifications”
This standard combines electrical safety tests with the IEC TR 62778:2014 methodology. This standard generally applies to more complicated light sources such as light engines.
The table below is based on Table 1 in IEC 62471-2 and includes the types of LEDs that are generally assigned a risk group based on particular tests.
Guidance on risk group exposure precautions for all of the calculations included in IEC 62471
The hazard exposure limits (EL) in IEC/EN 62471 are based on irradiance E (W/m2) and radiance L (W/sr-m2) values. With one exception, hazards that use L values as exposure limit criteria are related to light that is focused on the retina and hazards that use E values as exposure limit criteria are related to the surface of the eye or skin exposure. The exception is the “Blue light – small source” calculation. This is related to retinal damage but uses an E value as a surrogate for L to deal with mathematical complexities due to eye motion and small apparent source size. The subscripts identify which weighting factor was used to calculate the E or L value from the test data.
The added protection due to aversion response (about 0.25 seconds) gives visible light sources an added safety buffer so RG2 requires caution but RG1 does not. This is not the case for nonvisible light where there is no aversion response and, for nonvisible wavelength ranges, exceeding RG0 is cause for caution. Nonvisible light does not induce an aversion response, but the eye never stops moving so invisible light does have some eye motion protection incorporated in exposure limits. Risk group 3 exposure limits are based on light hazards that can cause damage in less than 0.25 second. The Sun is an example of an RG2 visible light source and has an LB blue light threshold limit value (TLV) of about one second. Staring at the Sun for longer than one second exceeds the exposure limit, but we are protected by aversion response so this does not generally happen.
This Sun example helps explain the use of the GLS test criteria in 62471 for white light sources and the potential replacement of GLS risk groups with the 62778 metrics. IEC 62471 defines general lighting service (GLS) lamps as: “Term for lamps intended for lighting spaces that are typically occupied or viewed by people. Examples would be lamps for lighting offices, schools, homes, factories, roadways, or automobiles. It does not include lamps for such uses as film projection, reprographic processes, "suntanning", industrial processes, medical treatment and searchlight applications.” These tend to be overhead light sources that are in the field of view for long periods of time but are not intended to be stared at.
The GLS test is the only test where the distance is different than 200 mm, the distance chosen as the close focus limit for retinal possible damage. The GLS test is performed at whatever distance has a 500-lux luminance for the light source. For white LED components, this distance generally ranges from 500 – 2500 mm depending on the brightness of the light source. This method has been criticized as being not very good at distinguishing safe levels at closer distances. For applications like overhead lighting where the eye level is further than the 500-lux distance, this is fine, and the preponderance of RG0 and RG1 ratings for GLS-white light sources should not be cause for concern.
IEC 62778 uses a different approach. Here the light source is measured at the same 200 mm distance as all other types of light sources and if the risk group exceeds “RG1 – unlimited” (safe for all applications and distances) the conditions to achieve RG1 are calculated. These conditions can be expressed as a lower drive current at 200 mm or as an RG1/RG2 boundary distance at the maximum current level calculated by the inverse square law.
To summarize
- RG3 is unsafe and significant engineering controls should be employed for these light sources
- RG2 is not immediately damaging and unless a situation occurs where a person stares at the light source, retinal damage is not likely for short exposures. An exposure hazard assessment should be conducted for RG2 light sources to identify what engineering controls are appropriate.
- Nonvisible RG1 sources should be treated the same as RG2 sources.
- Visible RG1 sources are considered safe by the standards
- All RG0 sources are considered safe by the standards.
- Retinal damage thresholds require one to look directly at the light source. These are identified by the radiance (L value) criteria in test reports.
- Skin and lens damage thresholds do not require looking directly at a light source but may be subject to a cosine correction (not covered by the standards). These are identified by the irradiance (E value) criteria in test reports. As discussed previously, the small source blue light hazard E value is a special case that should be treated as an L value.
- If a test is conducted at 200 mm and maximum drive conditions, all applications with lower currents and/or longer distances are safer than this worst-case test. These can be calculated using the inverse square law and datasheet information.
- GLS test results should only be relied upon for actual GLS applications.
- Most of the time a component level test can be transferred to a luminaire. The guidance in 62471-2 has a first attempt at clarifying this and 62778 has explicit designation of transferable results.
Related Eye Safety articles are found here:
Safety - Eye Safety Ratings of Luminus LEDs: What is IEC 62471 and how does it relate to IEC 62778?
Safety - Understanding IEC 62778 and Using KV,B to Calculate White Light Eye Safety Risk Groups
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