By Mark Smith 01/07/2026

Under: PPE and Workwear

EN ISO 16321-1 vs EN 166: The New Standard for Eye Protection Explained

EN 166 Is Changing – What Does It Mean for Construction Professionals?

Every day on construction sites across the UK, workers are exposed to hazards that can cause serious eye injuries. The use of tools like slab cutters, metal grinders, concrete drills, wall chasers, or even exposure to harmful chemicals serves to highlight that eye protection forms an integral part of personal protective equipment (PPE).

For more than two decades, EN 166 has been the accepted standard for eye protection in the workplace. Now, there is a move towards adopting an international standard: EN ISO 16321-1.

If you're a health & safety manager, site manager, contracts manager or PPE procurement specialist, understanding this transition is important for ensuring your workforce remains protected and your PPE specifications remain up-to-date.

What Is EN ISO 16321-1?

The EN ISO 16321-1 standard is the up-to-date international standard that sets out the requirements for eye and face protection equipment. It replaces EN 166:2001. This standard applies to the following types of personal protective equipment:

• safety glasses;
• safety spectacles;
• safety goggles;
• face shields; and
• visors.

The purpose of the standard is to ensure that all the new workplace hazards are taken into account, along with any new technologies and increased international consistency.
Why Has EN 166 Been Replaced?

Construction sites have changed significantly since EN 166 was introduced in 2001.

Today's workforce uses more powerful cutting and grinding equipment, more specialised materials and increasingly complex PPE systems that must work together.

The purpose of the development of EN ISO 16321-1 includes the following:

• Representing the present reality of risks at work.
• Improving the effectiveness of fit assessment.
• Updating the methodology of testing.
• Introducing more detailed performance markers.
• Improving compatibility with other PPE.
• Customising standards internationally.

The result is a more comprehensive standard designed around the realities of modern workplaces.

What Are the Biggest Changes Between EN 166 and EN ISO 16321-1?

While many aspects of eye protection remain familiar, several important changes have been introduced.

Improved Fit Assessment and Headform Testing

One of the most significant developments is the introduction of additional headform testing. Headform refers to the shape, size, and contours of an individual's head, which can affect how well safety equipment such as hard hats, helmets, and respiratory protective equipment fit and perform.

In the past, test methods were reliant upon a small number of headform sizes. However, according to EN ISO 16321-1, there is an increased need for improved assessment methods. 

Manufacturers are now required to specify what kind of headform and size were used when testing took place, and this should be clearly stated on the frame of the product. 

Such improvements allow for a more comprehensive assessment and testing of products. This change will particularly interest construction industry workers that combine hard hats, hearing protectors, and respirators with eye protection.

Updated Product Markings

One of the most noticeable changes will be the new marking system. The new standard provides more information to help users identify the protection offered by particular products. Familiarity with these markings can help in the accurate selection of eyewear for site-specific hazards.

New Chemical Resistance Classification

Chemical resistance is now available for the frame and the lens according to EN ISO 16321-1. Products meeting the requirements will be marked with a specific CH marking.

This is particularly relevant for workers handling the following:

• Resins
• Adhesives
• Solvents
• Concrete treatments
• Sealants
• Cleaning chemicals

For many construction environments, this provides clearer information than was available under EN 166.

Changes to Liquid Protection Markings

The marking 3 under EN 166 identifies protection against liquid droplets and splashes. Liquid protection now has its own specific marking 6 according to EN ISO 16321-1, shown on the frame. This change will help to identify products that are designed to provide protection against liquid hazards commonly found on construction sites.

Revised Impact Resistance Classifications

Impact protection remains one of the most important performance requirements for construction eye protection. 

Under EN 166, impact ratings included:

• F – Low Energy Impact (45 m/s)
• B – Medium Energy Impact (120 m/s)
• A – High Energy Impact (190 m/s)

Under EN ISO 16321-1, the classification system has been revised, and users may encounter different impact markings on products.

Health and safety professionals should not just rely on the well-known EN 166 markings but need to be aware of the performance requirements of the eyewear being specified.

This is particularly important for:

• Grinding operations
• Demolition activities
• Steel fabrication
• Concrete cutting
• Masonry work

Electrical Arc Marking Has Been Removed

Under EN 166, electrical arc protection was identified using the marking 8. Under EN ISO 16321-1, this marking no longer exists and has not been directly replaced.

Where protection from electrical hazards is required, product specifications should be carefully reviewed by electrical or utilities or infrastructure organisations, and manufacturers consulted.

New Radiant Heat Resistance Testing

EN ISO 16321-1 also includes testing related to radiation heat exposure. This tests the effect of the heat from a heat source on the inner and outer surfaces of the lens.

While not relevant to every construction project, it may be important for workers involved in:

• Hot works
• Asphalt operations
• Metal fabrication
• Utilities maintenance
• Industrial maintenance environments

Lens Compatibility Information

Another new requirement is that frames must indicate which lens versions they are compatible with. This improves traceability and helps users ensure components remain compliant when maintenance or replacement is required.

Understanding EN ISO 16321-1 Markings

The table below highlights some of the key differences between EN 166 and EN ISO 16321-1. 

Feature	EN 166	EN ISO 16321-1
Liquid Protection	Marking 3	Marking 6
Chemical Resistance	Limited classification	CH marking available
Headform Information	Not displayed	Displayed on frame (1,2,S,M,L)
Lens Compatibility	Not required	Displayed on frame
Radiant Heat Testing	Not included	Displayed on frame (T)
Electrical Arc Marking	8	Removed

Understanding these changes will become increasingly important as manufacturers transition product ranges to the new standard.

Does Existing EN 166 Eye Protection Still Comply?

Yes, the introduction of EN ISO 16321-1 does not mean existing EN 166-certified eyewear automatically becomes non-compliant.

Provided the product:

• Remains within its certification validity period
• Is suitable for the identified hazards
• Is correctly maintained
• Fits the wearer appropriately

it may continue to be used. There is currently no legal requirement to replace compliant EN 166 eye protection solely because the standard has changed. Existing EN 166 certificates remain valid until their expiry, which could be as long as November 2029, depending on the manufacturer's guarantee. 

What Does UK Law Require Employers to Do?

The standard does not constitute a legal obligation. Employers need to continue to comply with existing UK health and safety legislation, including:

Health and Safety at Work etc. Act 1974

Employers must ensure, so far as is reasonably practicable, the health, safety and welfare of employees. Learn more. 

Personal Protective Equipment at Work Regulations 1992 (As Amended)

Employers must provide suitable PPE where risks cannot be adequately controlled through other measures. Learn more. 

Management of Health and Safety at Work Regulations 1999

Employers must carry out suitable and sufficient risk assessments and implement appropriate control measures. In practical terms, it means selecting the eye protection appropriate to the hazards present, not just seeking certification markings. Learn more. 

What Does the HSE Say About Eye Protection?

The Health and Safety Executive (HSE) advises that employers should provide suitable eye protection wherever there is a foreseeable risk of eye injury.

The HSE also stresses the importance of:

• Correct PPE selection
• Compatibility with other PPE
• Proper maintenance
• Worker training
• Ongoing supervision

The introduction of EN ISO 16321-1 does not alter these fundamental principles.

Expert Advice for Construction Health & Safety Managers

The most common mistake organisations make when reviewing PPE standards is focusing solely on certification markings.

In practice, eye protection is only effective when:

• The correct hazard has been identified
• The product fits properly
• Workers wear it consistently
• It is compatible with other PPE
• Damaged equipment is replaced promptly

The switchover to EN ISO 16321-1 should therefore be viewed as an opportunity to reassess the PPE selection processes and not just as a change in the product specification.

Questions to Ask Your PPE Supplier

When reviewing eye protection specifications, ask:

• Is this product certified to EN ISO 16321-1?
• Does it protect against our specific site hazards?
• Is chemical resistance available where required?
• Has the eyewear been tested alongside hard hats and RPE?
• What impact resistance classification does it achieve?
• Are anti-fog and anti-scratch options available?
• Are replacement lenses and components available?

These discussions can help ensure compliance and improve worker acceptance of PPE. The move from EN 166 to EN ISO 16321-1 represents the most significant update to occupational eye protection standards in more than two decades. While existing compliant EN 166 products remain valid for now, future certifications will increasingly fall under EN ISO 16321-1.

For construction businesses, the key priority remains unchanged: selecting suitable eye protection based on risk assessment findings and ensuring workers are protected against one of the most common causes of preventable workplace injury.

All our eye protection products are manufactured to meet the requirements of the European Personal Protective Equipment (PPE) regulations and are clearly marked to indicate their fields of use and performance levels. Whether you need protection against impact, dust, liquid splashes, molten metal, or optical hazards, you can find compliant safety eyewear suitable for your task in our online shop. Browse our full range today to ensure you have the right level of protection for your workplace and industry requirements.