Eye and Face Protection: How to Read EN 166 Markings
Eye injuries happen in a fraction of a second: a chip from a grinder, a splash of chemical, the flash of a welding arc. The markings printed on safety glasses, goggles and face shields tell you exactly which of these they can stop. This guide explains how to read them.
The short answer: safety glasses (F) for flying particles. Goggles for dust, chemical splashes and liquids. A face shield (B or A) for grinding, cutting and splashes to the whole face, worn over glasses or goggles. A welding shield with the right shade for any arc welding. Look for EN 166 on all of them.
How to read the EN 166 marking
The frame and the lens each carry a short code. A lens marked 2C-1.2 W 1 FT KN or a frame marked W 166 FT CE reads like this:
| Marking | Meaning |
|---|---|
| 1, 2 or 3 (lens) | Optical class. 1 is best, for all-day wear. 3 is for occasional use only |
| S | Increased robustness: a steel ball dropped onto the lens |
| F | Low-energy impact: particles at 45 m/s. Typical for safety glasses |
| B | Medium-energy impact: 120 m/s. Goggles and face shields only |
| A | High-energy impact: 190 m/s. Face shields only |
| T | The impact rating also holds at extreme temperatures |
| 3 (frame) | Liquids: droplets (goggles) or splashes (face shields) |
| 4 (frame) | Large dust particles |
| 5 (frame) | Gas and fine dust |
| 8 (frame) | Short-circuit electric arc |
| 9 (frame) | Molten metal and hot solids |
| K | Lens resists scratching |
| N | Lens resists fogging |
The lower impact grade of frame and lens is the one that counts. A frame marked F with a lens marked B gives F protection.
Lens filters: clear, dark and welding
The number before the dash on a lens tells you its filter type:
- 2- or 3- (EN 170): ultraviolet filter. Clear lenses for general work.
- 5- or 6- (EN 172): sun-glare filter. Dark or mirrored lenses for outdoor work in strong sun.
- Shade number alone, such as 5 or 11 (EN 169): welding filter.
Browse safety glasses and goggles
Choosing by the hazard
Flying particles: drilling, cutting, general workshop
Safety glasses marked F, with side protection. Wrap-around styles stop particles coming from the side. For people who wear prescription glasses, over-spectacles (OTG) fit over their own frames.
Grinding and heavy cutting
A face shield (B) over safety glasses. Grinding throws particles hard enough to break ordinary lenses and hit the face below the glasses. See workshops.
Chemicals and liquids
Goggles marked 3 seal around the eyes. Glasses are not enough, because splashes run in around the frame. For pouring and mixing, add a face shield marked 3 over the goggles. See the chemical hazards guide.
Dust
Goggles marked 4 for coarse dust, and 5 for fine dust and gas. Indirect-vent goggles keep dust out while reducing fog.
Welding and cutting
Welding light burns the eye in seconds ("arc eye"), and it also burns the skin. Arc welding needs a welding helmet or shield (EN 175) with the right filter shade:
| Work | Typical shade |
|---|---|
| Helpers and people nearby, light glare | 1.7–3 |
| Gas welding, brazing and cutting | 4–7 |
| Arc welding (stick, MIG, TIG) | 9–14, rising with the current |
Auto-darkening helmets (EN 379) switch from a light shade to the welding shade in a fraction of a second, so the welder can see the work before striking the arc. Most cover shades 9–13. Always check the shade table that comes with your helmet. See heat hazards.
Outdoor work in strong sun
Tinted or mirrored lenses (5- or 6-) cut glare and UV for site, road and port work. Do not use them indoors or at night.
Comfort decides whether they are worn
The best glasses are the ones that stay on. Look for N (anti-fog) for hot and humid work, adjustable arms, a soft nose bridge, and a style workers are happy to wear. In Egyptian heat, fogging is the main reason glasses come off.
Emergency eyewash
Where chemicals are used, an eyewash station must be within a few seconds' reach. Flush the eye with clean water for at least 15 minutes, then get medical help. Portable bottle stations (EN 15154-4) give first response, and a plumbed station is best where chemicals are handled daily.
Questions buyers ask us
Are ordinary prescription glasses enough?
No. Ordinary lenses can shatter on impact and have no side protection. Use over-spectacles or prescription safety glasses marked EN 166.
Do face shields replace safety glasses?
For impact, wear glasses or goggles under the shield. A shield protects the face, but particles can come in from below and the sides.
What does UV400 mean?
The lens blocks ultraviolet light up to 400 nanometres, which covers the UV in sunlight. It is useful for outdoor work, but it is not a welding filter.
Buying for a team
Most sites need clear glasses for everyone, goggles for chemical and dusty tasks, and face shields or welding helmets at the grinding and welding stations. Send the list through For Companies and we will quote within 24 working hours, with bulk prices from 20 pieces.