Short answer
RG stands for "Risk Group", from the international standard IEC 62471 and the corresponding Chinese standard GB/T 20145, Photobiological safety of lamps and lamp systems. For retinal blue-light hazard: RG0 (exempt) means no hazard within 10,000 s (about 2.8 h) of direct viewing; RG1 (low risk) no hazard within 100 s; RG2 (moderate risk) no hazard within 0.25 s, relying on the natural aversion response to bright light; RG3 (high risk) may be hazardous even for momentary exposure. For classroom lighting under GB 7793-2025: general lighting luminaires must be RG0, and writing-board (blackboard) luminaires RG0 or RG1, effective from 1 November 2026.
Risk groups at a glance (retinal blue-light hazard)
| Group | Meaning | Direct-viewing time without blue-light hazard | Blue-light weighted radiance LB limit |
|---|---|---|---|
| RG0 Exempt | No photobiological hazard | 10,000 s (about 2.8 h) | <100 W·m⁻²·sr⁻¹ |
| RG1 Low risk | No hazard under normal behavioural limitations | 100 s | <10,000 W·m⁻²·sr⁻¹ |
| RG2 Moderate risk | Protected by the aversion response to bright light | 0.25 s | <4,000,000 W·m⁻²·sr⁻¹ |
| RG3 High risk | Hazardous even for momentary exposure | Less than 0.25 s | Above the RG2 limit |
Source: IEC 62471:2006, Chapter 6 classification rules.
FAQ
1. What does RG classification measure?
It measures the potential photobiological hazard of a light source to the eyes and skin, covering ultraviolet, near-ultraviolet, retinal blue-light, retinal thermal and infrared hazards; the classification is set by the most severe category. In lighting, the one most often discussed is retinal blue-light hazard: possible photochemical damage to the retina from staring at a bright source for a long time.
2. Does RG1 mean unsafe?
No. IEC 62471 states that the classification only indicates potential risk; whether there is an actual hazard depends on how the product is used, the exposure time and the luminaire itself. RG1 means that under normal behaviour people do not stare at it long enough for it to be a hazard. General lighting luminaires are assessed at the distance that produces 500 lx (and not closer than 200 mm).
Classroom general lighting requires RG0 because students spend long hours in classrooms and are young, so the standard takes a more conservative threshold for them.
3. What does the Chinese national standard require for classroom luminaires?
GB 7793-2025, clause 5.2.3: luminaires that are not exempt from retinal blue-light hazard assessment under GB/T 7000.1 shall be assessed per GB/Z 39942; writing-board local lighting luminaires shall be RG0 or RG1, and classroom general lighting luminaires shall be RG0. The test method follows GB/Z 39942 (6.6). The previous GB 7793-2010 had no such requirement.
4. Is a lower colour temperature automatically safer for blue light?
Generally, at the same luminance a higher colour temperature contains more blue, but the RG group must be determined from the measured spectrum and luminance, not colour temperature alone. GB 7793-2025 limits standard classrooms to 3300 K–5300 K (5.2.1), so a "low colour temperature" is not a way around blue-light testing; luminaire selection still depends on the risk group stated in the test report.
5. How to check during procurement?
- Ask suppliers for a blue-light hazard test report issued per GB/Z 39942 (or GB/T 20145), and check the stated group and that it covers the exact luminaire being offered.
- General lighting luminaires: RG0; board lights: RG0 or RG1.
- In the same report, also check colour temperature, Ra and R9, flicker index and SVM. These are all GB 7793-2025 requirements; passing one item does not mean the whole luminaire complies.
6. Does this apply to desk lamps and "eye-care" lamps at home?
GB 7793-2025 covers classrooms. Home study lamps fall under a separate set of standards not covered here. When choosing one, you can likewise check whether RG0 is stated and backed by a test report.
GKC can help schools review the test reports of existing luminaires, carry out classroom light-environment assessments, and support luminaire selection and delivery to the new standard. Contact us through the inquiry form on our website or at info@mail.gkc.ink.
References
- IEC 62471:2006 / EN 62471:2008, Photobiological safety of lamps and lamp systems, classification rules (Chapter 6): https://www.lisungroup.com/wp-content/uploads/2020/02/EN62471-2008-Standard-Free-Download.pdf
- Summary of exposure times by group: https://labino.com/wp-content/uploads/2020/10/IEC-EN-62471.pdf
- LB limit table (citing IEC 62471-1:2006), Radioprotection journal: https://www.radioprotection.org/articles/radiopro/full_html/2017/04/radiopro170025/T1.html
- GB 7793-2025 full text, National Disease Control and Prevention Administration: https://www.ndcpa.gov.cn/jbkzzx/c100202/2019767782478352384/DfuK7Vv3.pdf