eyewear specifications


Understanding EN166 - Personal Eye Protection Standard


Thousands of accidents involving eyes occur at work every single year. Although some of these incidents are minor and short-term, others (around 10-20%) result in partial or full blindness.

With serious damage to lifestyle and health at risk, employers are expected to provide their employees with suitable personal protective equipment to reduce the risk of injury. In accordance with Regulation (EU) 2016/425, all PPE must be tested and marked to prove that it can meet the relevant protective standards.

Protective eyewear is tested to meet a specific set of standards and is marked according to its protective ability. Although there are many standards for safety eyewear dependent on its purpose, all eyewear intended for use in the workplace must meet a core European standard: EN 166:2001.

In this guide, we cover the requirements of EN 166 and other standards related to eye and face protection.


When is safety eyewear needed?

Eye protection is required whenever there could be a risk to the eyes. The EN 166 standard of eyewear isn’t limited to the workplace.

Protective eyewear is diverse and is designed to counter a variety of risks such as splatter, impact and light filtration. UV rays from the sun is one of the biggest risks to the eyes.

To protect the eye from foreign objects, such as dust particles, caustic fluids, radiochemicals or metal swarf shavings, suitable eye protection should be selected and worn where applicable.

Eyewear is one of the most common forms of PPE and one of the most versatile. Where there is a potential hazard, eye protection should be worn even if there is no immediate, presentable risk. Some injuries are immediate, but others can be gradual as a result of lengthened exposure to sunlight, for example.

Protective eyewear tends to be split into four categories: safety spectaclesgoggles, visors/face shields and sunglasses.


What is EN166?

EN 166:2001 is the European standard covering the requirements for protective eyewear. It is closely linked to EN 167:2001 and EN 168:2001 which specify the optical and non-optical test methods.

EN 166 specifies the minimum requirements for a range of performance tests. This standard contains a set of requirements referred to as ‘basic requirements’, which may be regarded as mandatory.


Manufacturing EN 166 compliant eyewear

  • Eye protectors should be free from projections, sharp edges or other defects, which are likely to cause discomfort or injury during use.
  • No parts of the eye protector which are in contact with the wearer shall be made of materials that are known to cause any skin irritation.
  • Headbands must be at least 10mm wide over any portion which may come into contact with the wearer’s head. Headbands shall be adjustable or self-adjusting.
  • EN166 eyewear must be tested to pass the appropriate standards. These processes are outlined by the specifications of EN167 and EN168.
eyewear safety


EN166 eyewear testing – EN167 & EN168

Safety should be a priority in the workplace and testing for it ensures that risks are challenged before PPE is given to the wearer. Testing eyewear should be practised for eyewear intended for all applications — from DIY environments to heavy industry.

Below are the outlines of the requirements that need to be met in order to comply with eyewear standards:


EN 167 – Optical Tests

EN 166 requires optical assessment of the lens or faceshield under EN 167. This includes tests for the field of vision, transmission and diffusion, and refractive properties.

The main purpose of these tests is to ensure the eyewear does not impede or distort the vision of the user. It also makes sure the eyewear allows sufficient light through to the wearer’s eyes. The field of vision test is intended to ensure that nothing in the frame or the periphery of the lenses reduces vision.

Exposure to UV light can affect the transmission properties of safety glasses. These properties are measured again after the eyewear has been exposed to UV light. To meet the requirements, the transmission results must not exceed an impairing amount.

The final test procedure in EN 167 is the test for assessing the quality of the materials and surface. Defects likely to impair vision can be easily spotted using such equipment. Defects are permitted within 5mm of the frame, but not elsewhere across the lenses.


EN 168 Non-optical tests

Further non-optical tests must be carried out under EN 168, including robustness and resistance to heat, ignition and corrosion. There are two robustness tests – ‘minimum robustness’ and ‘increased robustness’.

The minimum robustness test involves placing a static load of 10kg on the centre of an ocular (lens) resting on a support plate. The ocular must not sustain any damage that results in cracking through the entire thickness, or cracking into two or more pieces. Fragments of 5mg or more must not become detached from the lens. The minimum robustness test is only applicable to cover plates or to filtering oculars.

Increased robustness: This test can be used on complete eye protectors, and involves dropping a steel ball onto the eyewear. For complete eyewear, the test is carried out with the eyewear mounted on a head form marked with the centres of the pupils and the exterior protection points.

As with the minimum robustness test, the ocular must resist substantial deformation. The frame must also resist breaking into two or more pieces or breaking such that the lenses are no longer contained.

For eyewear designed for use where risks from molten metal are present, a test is carried out to make sure eyewear can withstand the heat e.g. 100g of molten grey iron at 1450ºC and aluminium at 750ºC.

To test the penetration levels of molten metal, a 6mm ball bearing heated to 900ºC is applied to the lens to see how long it takes to pass through the material.

Eyewear is also tested against ignition. To see if eyewear can withstand ignition, a 6mm diameter x 300mm length steel rod pre-heated to 650ºC is pressed to eyewear. If the glasses don’t ignite or glow, it passes the test.

For the strength of frames, the arms and frame are flexed for 500 cycles (40 per minute). To pass this test, the products must have no fractures or permanent damage.


Related eyewear safety standards

·    EN ISO 4007:2018 (Replaced EN 165:2005): Personal protective equipment – Eye and face protection – Vocabulary


·    EN 167:2001: Personal eye protection – Optical test methods


·    EN 168:2001: Personal eye protection – Non-optical test methods


·    EN 169:2002: Personal eye protection – Filters for welding and related techniques – Transmittance requirements and recommended use


·    EN 170:2002: Personal eye protection – Ultraviolet filters – Transmittance requirements and recommended use


·    EN 171:2002: Personal eye protection – Infrared filters – Transmittance requirements and recommended use


·    EN 172:1995: Personal eye protection – Sunglare filters for industrial use


·    EN 175:1997: Personal protective equipment – Eye and face protection during welding and allied processes


·    EN 379:2003+A1:2009: Personal eye protection – Automatic welding filters

·    EN 1731:2006: Personal eye protection – Mesh eye and face protectors


How is EN 166 eyewear marked?

The order of markings on frames where relevant is: Manufacturer’s mark; EN166; Fields of use; Mechanical strength.

Markings associated with the basic requirements only – for all protective eyewear:

Requirement Lens Symbol Frame Marking
Scale Number or Shade Number Required for filters only -
Manufacturer’s Identification Required Required
Number of the Standard   EN 166
Optical Class 1, 2 or 3  

Mechanical Strength

Minimum Robustness

Enhanced Robustness

If high-speed particle testing requirements are met, the S symbol is replaced by one of the symbols below.

Low Energy Impact

Medium Energy Impact

High Energy Impact


No symbol







No symbol







Particular/optional requirements and associated markings:

Requirement Lens Symbol Frame Marking
Droplets or splashes of liquids   3
Large dust particle   4
Gas and fine dust particle   5
Short circuit electric arc 8 8
Molten metals and hot solids 9 9
Resistance to surface damage by fine particles K  
Resistance to fogging N  
Enhanced infrared reflectance R  
Replacement oculars o  


Some of the tests in the above table are not suitable for all eyewear types. For example, the only valid tests for spectacles are those with a letter K, N or R. Spectacles cannot be tested for liquid splash or large dust particles, as they are unable to protect against those hazards.

The resistance to high-speed particle test is carried out on complete eyewear. It tests the oculars and the frame. The particle used for these tests is a 6mm diameter steel ball-bearing that weighs 0.86g.

Low energy impact (at a speed of 45m/s) is applicable to all types of protective eyewear, but the medium energy impact (at 120m/s) is only applicable to goggles and face shields.

The high energy impact test (at a speed of 190m/s) is only used for face shields. This test is usually carried out with the samples at ‘normal’ temperatures but can be carried out in extreme temperatures. In this version of the test, the eyewear is impact tested after conditioning at 55°C and -5°C.


How to choose protective eyewear

When you are looking for fit-for-purpose eye protection, look out for the CE mark and EN 166 markings. EN 166 certification will ensure that the eyewear has been tested in accordance with European standards and possesses the properties required for suitable protection.

The primary purpose of eyewear is to ensure eyes are protected against short-term and long-term injury. Hazardous substances in workplaces should be regulated to provide suitable levels of safety, but certain tasks can present further risks with the potential for significant damage.

EN 166 eyewear will provide the basic testing requirements, but for more specific tasks or increased exposure, eyewear that complies with further standards will be required.

If you require further guidance on EN 166 eyewear or other items of PPE, contact WISE Worksafe today.


EN 166 eyewear