EN ISO 16321 Explained: What the New Protective Eyewear Standards Mean for the EU and UK

For over 20 years, the EN 166:2001 standard has defined the benchmark for protective eyewear across Europe. However, this is changing.

A new standard was published in 2022/2023, the formal, legal replacement of EN 166:2001, with November 2025 being the date after which only the new standard (EN ISO 16321) will be used for new certifications.

The new EN ISO 16321 suite (with parts 1, 2 and 3) will introduce significant technical, testing, and marking changes that will directly impact manufacturers.

Going forward, the EN ISO 16321 suite will place protective eyewear on the EU and UK markets under:

• Regulation (EU) 2016/425 on Personal Protective Equipment
• The UK’s retained PPE Regulation 2016/425 (as amended for Great Britain)

In this article we will break down what has changed, what remains valid during transition, and what manufacturers, buyers and suppliers must now consider.

The Regulatory Position in the EU and UK

The EN 166:2001 remained harmonised in the EU until November 2024 and is designated in the UK, meaning it can still be used for CE and UKCA marking under current transition arrangements.

However:

• The EN ISO 16321 series has now been published
• It is harmonised in the EU
• It is expected to be formally designated in the UK
• It will replace several legacy standards including EN 166, EN 169, EN 170, EN 171, EN 172, EN 379 and EN 1731

For any organisation placing eyewear on the EU or GB market, compliance with the applicable PPE Regulation remains a legal requirement.

What are the three parts of EN ISO 16321?

The new suite consists of:

• EN ISO 16321-1:2022 – General requirements
• EN ISO 16321-2:2021 – Additional requirements for welding and related techniques
• EN ISO 16321-3:2022 – Additional requirements for mesh protectors
• ISO/DIS 16321-4 – In development (biological hazards)

Unlike EN 166, the scope is now more clearly defined:

Now Included

• Plano protective eyewear
• Prescription protective eyewear
• Occupational use
• Educational environments

Now Excluded

• Laser protection
• Live-working arc protection
• Sports eyewear
• Medical-use protectors
• Solar-only protectors
• Ionising radiation protection

Separate standards apply for those applications.

The Biggest Structural Change: New Headforms

One of the most impactful changes is the introduction of new Headforms from:

• EN ISO 18526-4:2020

Previously, EN 166 used just two Headforms (small and medium).

Now there are six:

These represent approximately 95% of the global population and affect:

• Field of view testing
• Impact testing
• Coverage measurements
• Fit assessment

The selected Headform must now be declared in user instructions - a new transparency requirement affecting documentation and conformity assessment.

Optical Requirements: What’s Changed?

1. Field of View

Testing now uses the Stoll Apertometer method, replacing the subjective ellipse-based method used under EN 166.

Why this matters:

• More objective measurement
• More reference points
• Reduced interpretation variability
• Additional criteria for driving use

This aligns eyewear assessment more closely with other PPE testing methodologies used internationally.

2. Luminous Transmittance

Under EN ISO 16321-1:

• Lenses without deliberate filter action must transmit >80% light
• Face shields >2 mm or multiple-glazed protectors: ≥75%

Note: Under EN 166:2001, the requirement was >74.4% for all lenses.

This represents a tightening of clarity expectations for standard lenses.

3. Scattered Light (Haze)

The new standard replaces small-angle scatter testing with a wide-angle scatter (haze) method (except for welding filters).

Important: Results from EN 166 cannot be carried forward. There is no direct correlation between the two methods.

Manufacturers transitioning products must retest.

Physical Requirements: Major Shifts

Basic Impact (Now Mandatory for All)

EN 166’s “increased robustness” has been replaced with a defined basic impact requirement.

Key changes:

Impact levels:

• C = 45 m/s
• D = 80 m/s
• E = 120 m/s

There are also new defined protection zones:

• OPZ (Orbital Protection Zone)
• EOZ (Extended Orbital Zone)
• FPZ (Face Protection Zone)

The higher the impact level, the larger the required coverage area.

High Mass Impact (New to European Framework)

Borrowed conceptually from ANSI Z87.1, this is new within the European system.

• 500 g pointed projectile
• Two impact points (frontal left and right)

Optional - but applicable if claimed.

Thermal Exposure

Equivalent to EN 166’s elevated temperature test, but:

• Duration doubled to 120 minutes

This increases robustness expectations.

Vent and Gap Penetration (New)

Openings must not exceed 1.5 mm when tested with a rigid rod.

This is particularly relevant for ventilated eyewear designs.

Expanded Optional Requirements

EN ISO 16321 introduces several optional performance claims, including:

• Anti-fog
• Surface damage resistance
• Dust and gas protection
• Molten metal resistance
• Radiant heat (new)
• Streams of liquids (new)
• Anti-reflective coating assessment (new)
• Explosive atmospheres (new)
• Chemical resistance (new)

These claims must be tested and documented if declared.

Marking Changes

The marking structure has evolved significantly.

For example:

• Impact levels C, D, E replace F, B, A (low/medium/high energy)
• HM added (high mass impact)
• CT, DT, ET denote temperature-conditioned impacts
• “CH” introduced for chemical resistance 

Manufacturers must review mould tools, lens engraving, and technical documentation to ensure correct marking under the new system.

Incorrect marking risks non-compliance under the PPE Regulation.

Welding and Mesh Protectors

EN ISO 16321-2:2021

Covers optical radiation, hot solids, and welding-specific hazards. Must be applied alongside Part 1.

EN ISO 16321-3:2022

Replaces EN 1731:2006. One key difference: revised aperture-count requirements.

Certification in the EU and UK

Any organisation placing protective eyewear on the EU or GB market must comply with:

• PPE Regulation (EU) 2016/425
• UK retained Regulation 2016/425 (as amended for GB)

Certification routes include:

• Module B (EU Type Examination)
• Module C2 or Module D (Category III PPE where applicable)

Notified Bodies (EU) and Approved Bodies (UK) remain required for applicable PPE categories.

During transition:

• EN 166 may still be used within harmonisation/designation timelines.
• EN ISO 16321 adoption requires full retesting.
• Technical Files must reflect the correct standard version.
• EU Declaration of Conformity (DoC) and UK DoC must reference the applicable harmonised/designated standard.

What Manufacturers Should Do Now

• Audit product scope against EN ISO 16321 exclusions.
• Review impact performance versus new steel ball and velocity requirements.
• Assess coverage zones under new Headform methodology.
• Plan full optical retesting (field of view + haze).
• Update marking and mould tools.
• Coordinate early with your Notified/Approved Body.

The transition is not a minor update - it is a structural rework of European protective eyewear requirements.

Final Thoughts

The shift from EN 166 to EN ISO 16321 represents:

• Global harmonisation
• More objective testing
• Increased performance expectations
• Expanded hazard coverage
• Stronger alignment with modern PPE risk profiles

For EU and UK manufacturers, the key is not just compliance - but managing transition timing, certification sequencing, and documentation accuracy under the PPE Regulation framework.

Source: BSI New Protective Eyewear Suite of Standards: EN ISO 16321 Parts 1,2,3

https://www.bsigroup.com/globalassets/localfiles/en-gb/product-certification/ppe-eye-wear/en-iso-16321-white-paper-230720.pdf

• Len Bridgeman 2026