Standard explainer · EN 166
Safety specs carry their specification etched on the lens and frame in a compact code — impact grade, splash and dust protection, optical quality, coatings. Learn five characters and you can read any pair on the shelf.
The system
EN 166 is the umbrella standard for personal eye protection. The lens marking covers optical class and impact/coating performance; the frame marking covers the fields of use. The characters that do the work:
Choosing
| Task | Wear | Look for |
|---|---|---|
| General site & workshop wear | Safety specs | 1 F K N — daily-wear class, particle grade, both coatings |
| Grinding, cutting, strimming | Goggles (or specs + shield) | B impact grade |
| Chemical splash, decanting | Sealed goggles | 3 (liquids), often with 4/5 for dusts |
| Dusty demolition, insulation work | Sealed goggles | 4 or 5 |
| Welding & hot works | Dedicated welding protection | Shade numbers under the welding filter standards |
The real-world bit
Eye injuries cluster around a familiar story: the specs were in a pocket because they'd fogged, scratched or pinched. That makes comfort and coatings safety features, not luxuries — anti-fog (N) for anyone moving between temperatures, anti-scratch (K) for kit that lives in a toolbag, and adjustable arms for the long-shift fit. Prescription wearers have real options: over-specs sized to fit across glasses, and prescription safety specs made to EN 166 — both beat the wear-nothing compromise.
Fit rules also apply upward: goggles must seal to earn their splash and dust codes, and a face shield is secondary protection worn over specs or goggles for the highest-energy tasks, not a substitute for them.
Buying
Questions
Impact protection against high-speed particles at 45 m/s — the standard grade for everyday safety specs. B (120 m/s) needs goggle construction, and A (190 m/s) a face shield. The letter counts only if both lens and frame carry it.
K is anti-scratch, N is anti-fog. They're the difference between specs that stay wearable and specs that end up in a pocket — which is where eye injuries happen. For daily wear, treat both as required.
Yes — prescription safety specs certified to EN 166 are a standard product, and over-specs that fit across ordinary glasses cover occasional use. Ordinary prescription glasses on their own are not rated impact protection.
When the hazard needs a seal or a higher impact grade: chemical splash (field-of-use 3), fine dust (4/5), or high-energy particles from grinding and cutting (impact grade B). Specs protect the front; goggles protect the perimeter.
Helmets, masks, eye protection, gloves and the rest of the PPE wall, certified and in stock.