Do I have to replace my EN 166 eyewear?

No. Eyewear already certified to EN 166 remains valid and may continue to be used and purchased. EN ISO 16321 replaces EN 166 gradually – new products are increasingly tested to the new standard, sometimes to both in parallel.

ISO 16321 harmonises markings worldwide and reassigns the mechanical strength letters. C equals the former F (45 m/s). The change is systematic – it creates room for the new intermediate class D so the sequence C – D – E reads in ascending order.

D is an entirely new impact class between C (45 m/s) and E (120 m/s), representing roughly 80 m/s. It closes a gap that did not exist under EN 166 and allows eyewear to be matched more precisely to the real risk.

HM stands for the tested head form. EN ISO 16321 tests six standardised head sizes from HM1 (small) to HM6 (very large), and the product states which sizes the protection was verified for. Fit becomes a verifiable part of protection.

CH marks protection against chemicals in the form of droplets and splashes – comparable to the former digit 3 under EN 166, but tested more clearly. Directed liquid jets are covered by the new JT marking.

What do U, G, W and R mean?

These letters replace the leading digits of the former filter standards: U for UV (EN 170), G for glare/sun (EN 172), R for infrared (EN 171) and W for welding (EN 169). The following number is the shade level.

Which markings remain unchanged?

K for scratch resistance, N for anti-fog, optical classes 1–3, the manufacturer marking and the CE mark under PPE Regulation 2016/425 all remain. Markings still appear on both lens and frame, complemented by user information and the declaration of conformity.

Standards knowledge centre

EN ISO 16321 – The new standard for eye protection

Find out what changes the new standard brings compared with EN 166 and what they mean for companies and users.

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2021: published
3: parts
6: head sizes

What is changing?

EN ISO 16321 consolidates and modernises the many European standards for eye and face protection.

Additional tests for risks that were not previously covered
Reassigned letters for mechanical strength (C, D, E)
Globally consistent requirements across countries and industries

4 coverage areas

instead of classification by product construction

Ball drop (basic requirement)
CLow energy impact 45 m/s
DMedium energy impact 80 m/s
EHigh energy impact 120 m/s

6 head sizes

for 95 % of all head shapes worldwide

1SSmall (European)
1MMedium (European)
1LLarge (European)
2SSmall (Asian)
2MMedium (Asian)
2LLarge (Asian)

Optional markings — for extended protection functions

Code	Description	Position
Additional markings
3	Protection against liquids (drops and splashes)
4	Protection against coarse dust with grain size > 5 µm
5	Protection against gases, vapours, mists, smoke and fine dust < 5 µm
6	Protection against high-pressure liquid jets (goggles and visors)new
7	Protection against radiant heat (950 K and 1450 K, visors only)new
8	Protection against electric arc flashnew
9	Protection against molten metal and hot solids (visors only)
CH	Chemical resistancenew
HM	Resistance to high-mass impactnew
T	Tested at extreme temperatures (−5 °C / +55 °C)
K	Surface resistance to small particles (scratch resistance)
N	Resistance to fogging
Filter markings
U	UV protection filternew
G	Sunglare filternew
W	Welding filternew
R	Infrared filternew
L	Signal light recognition (optionally certifiable in addition)new

Decoding the marking

Click any segment — we explain what it means.

Lens

Frame or temple

Manufacturer

Identification of the manufacturer or brand – «UG» for Unico Graber. Enables traceability to the product and its declaration of conformity.

Example marking — may differ depending on function, application and lens type.

What does this mean for you?

Employers

Standard-compliant selection of eye protection – legally documented and derived from the risk assessment.

Safety officers

Understand the new markings faster and train staff effectively.

Users

More safety, better fit and greater wearing comfort in daily use.

Frequently asked questions about EN ISO 16321

Comparison EN 166 ↔ EN ISO 16321

Area	Previously (EN 166)	New (EN ISO 16321)	Meaning
Mechanical strength	F	C	Impact at 45 m/s (6 mm steel ball)
Mechanical strength	—	D	New intermediate class: impact at 80 m/s
Mechanical strength	B	E	Impact at 120 m/s
Extreme temperatures	FT	CT	Impact also tested at −5 °C and +55 °C
Extreme temperatures	BT	ET	High impact resistance at extreme temperatures
Filters	2- / 3-	U	UV filter with shade number, e.g. U6
Filters	5- / 6-	G	Sun glare filter, e.g. G3
Filters	4-	R	Infrared filter, e.g. R4
Filters	EN 169	W	Welding filter, e.g. W10
Chemicals	3	CH	Protection against droplets and splashes
Liquid jet	—	JT	New: protection against directed liquid jets
Head size	—	HM 1–6	Tested head form/size, e.g. HM3
Durability	K	K	Scratch-resistant surface – unchanged
Durability	N	N	Anti-fog – unchanged

Unsure which eye protection matches your risk assessment?

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