Detailed Introduction to EN 170 Standard – Ultraviolet (UV) Protection for Eye Protection
1. Overview of EN 170 Standard
- Full Name: EN 170 – Personal Eye Protection: Ultraviolet (UV) Filters
- Purpose: Specifies the requirements for ultraviolet (UV) protection filters used in personal eye protection.
- Scope: Covers all types of protective eyewear, including:
- Safety glasses
- Safety goggles
- Face shields
- Welding visors
- Specialized lenses used in UV-intense environments
EN 170 ensures that UV-protective lenses effectively filter harmful ultraviolet radiation (UV-A and UV-B) while maintaining good optical clarity and avoiding distortion.
2. Importance of UV Protection in Eye Safety
- Ultraviolet radiation (UVR) from natural (sunlight) and artificial (industrial lamps, welding arcs) sources can cause serious eye damage, such as:
- Photokeratitis (temporary eye burns)
- Cataracts (clouding of the eye lens)
- Retinal damage
- Long-term vision impairment
Applications of EN 170-Certified Eyewear
- Industrial Work: UV exposure from welding, metalworking, and glassblowing
- Medical & Laboratory Use: UV sterilization, phototherapy, and UV lamp operations
- Outdoor Work: Construction, agriculture, and aviation where prolonged sun exposure occurs
- Electronics & Semiconductor Industry: UV curing and precision optical work
3. Key Requirements of EN 170
The EN 170 standard sets strict guidelines for UV protection levels, ensuring that safety eyewear:
✅ Effectively filters UV-A and UV-B radiation
✅ Maintains optical clarity with minimal distortion
✅ Does not excessively reduce visible light transmission
EN 170 lenses are marked with a UV protection scale number (2-1.2 to 2-5), which indicates the level of UV filtering and light transmission.
UV Protection Scale (EN 170 Marking)
| Scale Number | UV Protection Level | Light Transmission (%) |
|---|---|---|
| 2-1.2 | Low UV protection | 74.4 – 100% |
| 2-1.4 | Moderate UV protection | 65.2 – 74.4% |
| 2-1.7 | High UV protection | 57.2 – 65.2% |
| 2-2.5 | Very high UV protection | 29.1 – 57.2% |
- Lower numbers (2-1.2, 2-1.4): Allow more visible light, suitable for indoor UV protection.
- Higher numbers (2-2.5, 2-5): Block more UV light, ideal for outdoor and industrial applications.
4. Testing Methods in EN 170
EN 170 defines specific test methods to ensure that lenses meet UV protection requirements while maintaining high optical quality. The key tests include:
- Ultraviolet Transmission Test (UV Filtering Efficiency)
- Luminous Transmission Test (Visible Light Passing Through)
- Optical Quality & Distortion Test
- Color Recognition Test
- Material Durability Test (Aging & Stability Under UV Exposure)
A. Ultraviolet Transmission Test (UV Filtering Efficiency)
Purpose
- Measures how much UV-A (315-380 nm) and UV-B (280-315 nm) radiation is blocked by the lens.
- Ensures that the filter meets the required UV protection scale.
Test Procedure
- A controlled UV light source is directed through the lens.
- A spectrophotometer measures the amount of UV radiation passing through.
- The transmission values are compared to the standard’s UV protection scale.
Pass/Fail Criteria
- Lenses must block at least 99.9% of UVB radiation and meet the UV transmission limits for their respective scale number.
B. Luminous Transmission Test (Visible Light Passing Through)
Purpose
- Ensures that lenses provide sufficient visible light transmission while filtering UV.
- Prevents lenses from being too dark, which could affect visibility in work environments.
Test Procedure
- A white light source (simulating daylight) is directed through the lens.
- A photometer measures how much visible light passes through.
- The transmission percentage is compared to EN 170 requirements.
Pass/Fail Criteria
- Luminous transmission must fall within the defined range for each UV protection scale number.
C. Optical Quality & Distortion Test
Purpose
- Ensures that UV-filtering lenses do not introduce blurriness, visual distortion, or eye strain.
Test Procedure
- The lens is examined using an optical bench with a grid pattern behind it.
- The wearer looks through the lens to check for image distortion, blurring, or waves.
Pass/Fail Criteria
- The image must remain clear and undistorted.
- Lenses failing this test can cause eye fatigue, headaches, or difficulty focusing.
D. Color Recognition Test
Purpose
- Ensures that the lens does not alter color perception significantly.
- Essential for workers who rely on accurate color vision, such as electrical engineers and pilots.
Test Procedure
- A color chart with various shades (red, green, blue, yellow) is viewed through the lens.
- The observer determines if any colors are faded or altered.
Pass/Fail Criteria
- Lenses must allow natural color recognition, meaning they should not distort color perception.
- Welding lenses, which may have a slight tint, must still permit safe color identification.
E. Material Durability Test (Aging & Stability Under UV Exposure)
Purpose
- Evaluates whether prolonged UV exposure causes material degradation (yellowing, brittleness, cracking).
Test Procedure
- The lens is exposed to intense UV radiation (50 hours) using a UV lamp (280-400 nm wavelength range).
- The lens is checked for discoloration, cracking, or loss of UV protection properties.
Pass/Fail Criteria
- The lens must maintain its UV-blocking properties and optical clarity after prolonged exposure.
5. Marking & Certification of EN 170 Eyewear
Once a UV-protective lens passes EN 170 tests, it is certified and marked accordingly.
EN 170 Marking System
- UV Filter Scale Number (e.g., 2-1.2, 2-2.5)
- Optical Class (1, 2, or 3, indicating distortion levels)
- Manufacturer’s Mark (e.g., “Uvex,” “Bolle”)
- CE Marking (Compliance with EU Safety Standards)
For example, “2-1.2 1 CE” means:
- UV Filter: 2-1.2 (low UV protection, high visible light transmission)
- Optical Class: 1 (highest optical quality)
- Certified for European safety regulations (CE mark)
6. Comparison with Related Standards
| Standard | Focus | Key Features |
|---|---|---|
| EN 166 | General Eye Protection | Covers optical & mechanical safety |
| EN 167 | Optical Test Methods | Tests clarity, refraction, and lens quality |
| EN 168 | Non-Optical Test Methods | Evaluates heat, impact, and chemical resistance |
| EN 170 | UV Protection | Defines UV-filtering requirements |
| EN 172 | Solar Protection | Specifies sun glare protection for industrial eyewear |
7. Conclusion
The EN 170 standard is crucial for ensuring that safety eyewear provides adequate UV protection without compromising optical quality. Its strict testing methods guarantee that workers exposed to UV radiation can rely on high-quality, distortion-free, and durable eye protection.
