EN 166 – Understanding the Personal Eye Protection Standard

EN 166 - Understanding the Personal Protective Eyewear Standard

Here are some eye opening statistics.

The Government’s Labour Force data from 2021 put the number of reported eye injuries sustained at work at 4,410, and while HSE figures reveal that only around 1% of all reportable non-fatal injuries affect the eye, during that year 512 people sustained serious eye injuries including the loss of sight in one or both eyes. It is reported that only around 40% of the injured workers were wearing some form of eye protection when the accident occurred.

According to Manchester Royal Eye Hospital, 90% of all sustained eye injuries could have been prevented.

Among the hazards that can harm the eyes are flying objects, falling objects, sparks striking the eye, chemical splashes and radiation from welding equipment. Behavioural factors include taking risks or rushing to finish a job, carelessness, working when tired or under stress, inadequate training or knowledge on how to operate the tools and machinery that you are using, insufficient lighting in the workplace and poor eyesight not corrected by glasses.

Employers are legally required to provide every employee with the appropriate safety equipment, requisite for the job on hand, and fully compliant with the relevant safety standards. Different tasks will require different appropriate protection solutions, and care should be taken to identify the correct type of equipment, such as sun glasses, safety glasses, safety goggles or face-shields, and make certain it fits the wearer properly.


What is EN 166?

In this article, we examine the requirements for EN166 standard, the core European standard that applies to protective eyewear.

EN 166 establishes the minimum requirements for performance tests, including a set of mandatory criteria referred to as ‘basic requirements’.

Manufacturing Standards for EN 166 Compliant Eyewear

  • Protective eyewear must be free from defects such as projections, sharp edges or other intrusions, which could cause discomfort or injury during use.
  • Any part of the eyewear coming into contact with the wearer must be made of materials that are free of any known cause of skin irritation.
  • Headbands must be adjustable or self adjusting, and any section coming into contact with the wearers head has to measure at least 10mm wide.
  • EN166 eyewear must undergo testing to pass the appropriate standards. These processes are outlined by the specifications of EN167 and EN168.


Eyewear Testing – EN 167 and EN 168

Eyewear testing should be performed on eyewear intended for all projects — from DIY to heavy industry – to confirm that the relevant hazards are challenged and overcome before PPE is given to the wearer. Outlined below are the requirements that are met through a series of tests in order to achieve compliance with safety eyewear standards:

Optical Testing – EN 167

EN 166 requires an optical quality evaluation of the lens or face shield based on EN 167, which includes assessments for field of vision, refractive properties, and transmission and diffusion tests.

The primary purpose of these tests is to ensure the eyewear in no way impedes or distorts the vision of the wearer, and that there is no impediment to vision in the frame or periphery of the lenses. They also guarantee that sufficient light transmittance is allowed through to the eyes of the user.

Exposure to UV light can impact the transmission properties of safety glasses, which are then re-evaluated after exposure. To meet regulations, the transmission results should not exceed a harmful level.

The final test procedure in EN 167 involves assessing the quality of materials and surface. Certain identified defects are allowed within 5mm of the frame, but not elsewhere on the lenses.

Non-Optical Testing – EN 168

Under EN 168, there must be further testing to determine resistance to heat, ignition, and corrosion. There are also two checks on the quality of robustness – “minimum robustness” and “increased robustness”.

The minimum robustness test involves placing a 10kg load on the centre of an ocular (lens) on a support plate. The ocular must not crack through or into two pieces, and fragments of 5mg plus must not detach from the lens. This test is only for cover plates or filtering oculars. For increased robustness, a steel ball is dropped onto the eyewear. The eyewear is mounted on a head form with marked pupil centres and exterior protection points. The ocular and frame must resist deformation and not break into two or more pieces, or the lens detach form the fame.

Eyewear designed for use where molten metal is present must undergo testing to prove it can withstand 100g of molten grey iron at 1450ºC and aluminium at 750ºC. Penetration levels of molten metal are tested with a heated ball bearing (heated to 900ºC) and pressed against the lens. Eyewear is also tested for ignition resistance using a pre-heated steel rod pre-heated to 650ºC.

Frames are tested for strength by being repeatedly bent and flexed (500 cycles at 40 per minute). To pass, the product must not display any fracture or permanent damage.


Eyewear Safety Markings

The diagrams below outline the markings for the corresponding requirements for eyewear protection.

EN 166 - Understanding the Personal Eye Protection Standard

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Not all tests in the table are suitable for all types of eyewear. Spectacles can only be tested with certain tests labelled K, N, or R. They cannot be tested for liquid splash protection or large dust particles as they do not provide defence against those hazards.

The high-speed particle test is done on complete eyewear, including the oculars and frame, using a 6mm diameter steel ball bearing weighing 0.86g.

Low energy impact test (at 45m/s) applies to all protective eyewear, while medium energy impact test (at 120m/s) is only for goggles and face shields. High energy impact test (at 190m/s) is specifically for face shields, which are evaluated after conditioning at 55°C and -5°C in the extreme temperature version of the test.

For more information on this, visit this blog post published by Betafit.

This post from Bollé Safety is also helpful.


How To Choose the Correct Protective Eyewear

EN 166 safety standards should be implemented whenever there is a potential risk to the eyes. Protective eyewear covers a large range of products, specifically designed to guard against a variety of hazards including splatter, impact from foreign objects and light filtration. UV rays from the sun can also cause serious damage to the eyes. It is one of the most commonly used and multifunctioning forms of PPE, normally made to high levels of wearer comfort, and it should be used by default where any potential hazard may be.

Identification of fit-for-purpose eye protection is simplified by checking for the EN 166  certification markings. This will provide assurance that the correct standards and properties are included to provide suitable protection. It is important to be aware that while EN 166 approved eyewear provides fundamental  legal compliance and basic protection, specific tasks with higher risk levels or increased exposure may require PPE that complies with a higher protection levels.


Clad Safety works alongside key operators in the construction, rail and utility sectors, while providing streamlined PPE solutions to fast paced teams, from our wide range of innovative products.

For further technical advice and support around EN 166, guidance on the best personal eye protection for any project, or any other queries about safety regulations and optimal protection for your on team, please call 0800 161 3661 or email [email protected].


Safety markings diagram and feature image source – Uvex Safety