Twenty Twenty Vision

Avoiding (or preventing) eye injuries

by David McKeown

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Injuries to the eyes are among the most serious that workers can suffer, and can lead to serious consequences, such as permanent loss of sight. This damage can be the result of a single major event or caused gradually by, for example, prolonged exposure to ultraviolet (UV) light in the work environment. Many injuries to the eyes – whether sudden (traumatic) or gradual – can be prevented or significantly reduced by the provision and wearing of suitable personal protective equipment (PPE). SATRA PPE expert David McKeown provides an overview.

If used correctly, protective eyewear can prevent many injuries to the eyes. However, selecting suitable eyewear requires a thorough understanding of the risks within a specific workplace. Because of this, the first step to selecting correct eye protection (and, indeed, correct PPE in general) is to conduct a thorough risk assessment within the workplace to identify the hazards.

There are many hazards in the workplace that can affect the eyes and face. They can be collected together into a small number of categories – for instance, ‘heat/molten metal’, ‘mechanical’, ‘dust’, ‘chemical’, ‘electrical’ or ‘optical’. In addition, there are other more indirect hazards which may not be immediately obvious. As an example, eyestrain caused by eyewear with poor optical quality can lead to fatigue, which could make an accident such as a slip or trip more likely. Similarly, eyewear which is susceptible to fogging or misting (or is easily damaged by fine abrasive particles) can obscure vision, which again may lead to accidents such as slips or trips. If filtering eyewear does not permit good colour recognition, it might affect how a wearer perceives traffic lights or warning lights on instrument panels.

“selecting suitable eyewear requires a thorough understanding of the risks within a specific workplace”

Markings for protective eyewear

Once the hazards are identified, eyewear can be matched to specific hazards. Within the European Union (EU), all protective eyewear should be CE marked, and each product must be marked on both the ocular (lens) and the lens surround and/or frame with markings indicating the type of protection provided. The current standard in Europe for most types of eye protectors is EN 166:2001. This specifies the requirements for such products in the form of spectacles, goggles and face protectors – for instance, visors and facemasks. There are other more specialised standards for specific types of eye and face protectors, specifically EN 175 for welding masks and shields, and EN 1731 which covers mesh-type eye and face protectors.

Table 1 provides an explanation of the markings to be used on both the lenses and the frames. The markings indicate hazards and, where appropriate, the level of hazard against which the eyewear will protect the wearer. It is important to realise that EN 166:2001 also specifies the order in which markings must appear, and also that some specific markings apply to the lens only, some to the frame only and others to both the frame and the lens. In the case of eye protectors in which the lens and frame form a single unit, all the marking should be on the frame.

Markings for filtering lenses

The markings on the ocular should always include a code or trademark representing the manufacturer. To the left of this mark is the scale number or shade number if present. If there is neither a scale nor a shade number, it may be assumed that the eyewear offers no protection against optical hazards. If there is a ‘scale number’, it will usually be given in the form of ‘code number – shade number’ (for instance, ‘4 – 10’).

Table 2 shows a list of the code numbers used for most filtering lenses. In the case of welding filters, there is only a shade number (no code number). The shade number is representative of the level of luminous transmittance for the filter. Shade numbers in the range 1.2 to 16 are recognised in EN 166, where a shade number of 1.2 would apply for a luminous transmittance from 100 per cent to 74.4 per cent down to a shade number of 16, which would apply for a luminous transmittance from 0.000061 per cent to 0.000023 per cent.

The higher the shade number, the greater the amount of optical radiation that is absorbed by the lens, and the greater the protection from intense optical radiation in the ultraviolet, visible and infrared bands. For welding operations, EN 169 (the standard which specifies the performance of welding filters) recommends specific shade numbers based on the type of welding operation being performed and the level of electric current used in the welding process. Similarly, EN 171 (the standard which specifies the performance of filters protecting against infrared hazards) recommends specific scale numbers depending on the temperature of hot objects (such as ovens, moulds, presses and furnaces) present in the environment.

For example, a filter with a scale number of 4 – 1.2 will protect against the thermal radiation emitted by a hot object at a temperature up to 1,050°C, whereas a scale number of 4 – 10 will protect against the thermal radiation from an object with a temperature of up to 2,220°C.

Optical class

Immediately to the right of the manufacturer’s identification mark is the optical class. The highest level is class 1, with class 3 being the lowest level. The optical class of the lens depends on the magnitude of any spherical, astigmatic and prismatic refractive powers. It is clearly desirable that the optical power of any protective lens or visor is as close to zero as possible. In practice, however, this is not always achievable. Any flat, uniform sheet of transparent material may gain unwanted refractive powers simply by bending it (which would be necessary in order to fit it to the lens holder or head mounting device). Moulded items, such as the majority of spectacle and goggle lenses, have curves built in so that they wrap around the eye region of the face. The thickness of moulded lenses can also vary across the lens, and again such physical effects can introduce refractive powers.

Mechanical strength

After the optical class, the next marking in the lens marking indicates ‘mechanical strength’. As a minimum, all occupational eye and face protectors according to the three main European standards for eye/face protectors (EN 166, EN 175 and EN 1731) must carry the ‘S’ marking, which shows that the whole eye protector has achieved the minimum requirements in the increased robustness test. Such eyewear should be capable of coping with some rough handling – for example, knocks and dropping onto the floor, as well as coping with impacts from small, lowspeed particles.

Higher levels of mechanical protection are indicated by the ‘F’ marking, indicating low-energy impacts, the ‘B’ marking (mediumenergy impacts) and the ‘A’ marking, indicating high-energy impacts. Where this testing has been carried out after the eyewear has been conditioned at extreme temperatures before the impact test, the marking is amended to ‘FT’, ‘BT’ or ‘AT’.

These markings indicate that the eye/ face protector has successfully met the requirements for high-speed particles, in which a small metal ball of mass 0.86g is fired at the whole eye protector. The 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 applicable to face shields. This test is usually carried out with the samples at ambient temperatures but, as an option, it can be carried out on samples exposed to extreme temperatures. In this version of the test, the eyewear is impact tested after conditioning at 55°C and -5°C. The criteria for passing or failing in the high-speed impact test are the same as for increased robustness.

Where the eye/face protector achieves one of the high-speed particle test ratings, the ‘S’ marking on both lens and frame is replaced by ‘F’, ‘FT’, ‘B’, ‘BT’, ‘A’ or ‘AT’ as appropriate.

After the mechanical code, the lens marking will include, if appropriate, the codes for protection against electric arc (‘8’) and protection against molten metal and hot solids (‘9’). If required, these two tests must be conducted on whole eye/ face protectors and both the lens and the frame/visor carrier will show the ‘8’ or ‘9’ marking if testing was successful. Only face shields will be marked with an ‘8’ and only if the complete eye/face protector has been tested in accordance with the additional arc rating requirements given in the German standard GS-ET-29. Although not specified in EN 166, the EU notified body vertical group for eye and face protection recommends testing to this standard if the manufacturer wishes to place the ‘8’ marking on the protectors. An arc incident is one of the most serious workplace accidents and if a risk assessment highlights the risk of arc flash, appropriate PPE must be worn for all areas of the body at risk – that is, the head, face, torso, arms and hands. Arc incidents often occur while working on a live electrical installation. Therefore, the worker would probably be facing the installation and would likely be only an arm’s length away from it.

Protection against molten metal and hot solids (marking ‘9’) can only be claimed for goggles or face shields. In the test, the material of the lens must prevent adherence of molten iron and molten aluminium to the lens surface. The lens material must also be capable of resisting penetration by a ball bearing (heated to 900°C) for at least five seconds.

Other markings apply only to the lenses and not to the frames. A ‘K’ marking indicates resistance to surface damage by fine particles and an ‘N’ marking indicates resistance to fogging. Both sets of requirements are optional and neither are related directly to preventing eye injuries. However, the ‘K’ marking (if present) indicates that the eyewear will remain free from surface marking or scratches which might degrade vision. Similarly, if the eyewear is prone to fogging, this can also interfere with vision in certain circumstances – for instance, if the wearer goes indoors after a prolonged period outside. Any interference with vision could put the wearer at risk from other hazards.

A further mark that should be used following the marking for mechanical strength is ‘R’, which indicates an enhanced reflectance in the Infrared. Eyewear displaying this marking would be expected to reflect at least 60 per cent of incident infrared radiation, which should help wearers to remain comfortable while working in high temperature environments such as foundries.

Finally, the original lenses for eye protectors where the lenses can be changed, should be marked ‘0’ and replacement lenses marked with ‘v’.

This concludes the marking that would appear on the lens of protective eyewear. The frames must also carry marking codes. Some of these are the same codes which appear on lenses, although there are exceptions. Only markings relevant to frames would be included – there would be no markings relevant to optical quality or filtering properties used on a frame.

With respect to frames, the marking begins with the identification mark or trademark of the manufacturer. To the right of this will be the standard number which, if appropriate, is followed by the field-of-use markings. These latter markings are to highlight resistance to i) penetration by liquids, ii) large dust particles, iii) fine dust particles and gases, iv) protection against arc flash and v) resistance to molten metal (if appropriate). Note that none of these fields of use markings can ever appear on spectacle frames as these cannot protect against particles and gases.

The first three ‘field of use’ markings which might appear on the frame relate to hazards where it is necessary for the frame to seal to the eye area (such as goggles), or provide an enhanced area of protection. Eyewear intended to protect against the ingress of liquid droplets or splashes must be able to seal the eye area or provide sufficient coverage to the whole face. Such eyewear would be marked ‘3’ on the frame but not the lens. For protection against gases and fine or large dust particles, only goggles which seal against the perimeter of the eye area of the face are permitted. If protection is offered against large dust particles, the frames must be marked with a ‘4’ and with a ‘5’ if protection is offered against fine dust particles and gases. If the ‘8’ and ‘9’ markings appear on the frames, these have the same meaning as when they are on the lenses as described earlier in this article, that is, protection against arc flash and resistance to molten metal.

“all PPE for a work environment should be checked before each use for damage or deterioration”

Next in sequence will be the marking indicating the type and class of mechanical protection. The definitions of these markings are as previously described for lenses. An ‘H’ following the mechanical protection mark indicates that the frame is intended to fit a small head. Finally, if applicable, the highest ocular scale number compatible with that frame is to be marked.

Where eye protectors are formed from a single unit combining lenses and frame, the marking should be on the frame. The markings should appear in the following order:

All applicable lens markings followed by

  • the number of this standard (for example, EN 166), then
  • the appropriate fields of use codes, followed by
  • the applicable mechanical protection code

The key to avoiding eye injuries is to carry out a thorough risk analysis in order to highlight the specific hazards present, categorising them as mechanical, electrical, chemical and so on. Then, eyewear should be selected that shows the appropriate codes marked on the lens and frame. If available, the instructions for use should also be read, as these may contain more information on protections against specific hazards.

In conclusion

This article has covered the marking requirements for protective eyewear, what the individual markings mean specifically in relation to products sold on the EU market and marked in accordance with EN 166:2001. Before placing any product on the market (at least in Europe), manufacturers and distributors must ensure that their products are tested and CE-marked to the correct standards and that labelling and information for users carries the information necessary for safe use.

For non-European markets, testing should be carried out to the appropriate standards required by those markets – whether ISO, ANSI, AS/NZS or others. Users of PPE should also check that the product issued to them is sufficient to mitigate for the potential hazards identified in their workplace by risk assessments. In addition, all PPE for a work environment should be checked before each use for damage or deterioration, and replaced if there is the slightest doubt about its ability to protect.

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