Protecting eyes, ears and head
Explaining the different standards that apply for each aspect of protection for the eyes, ears and head.
Image © Anze Furlan/psgtproductions
People in the workplace often face multiple hazards at the same time. For example, a tree surgeon using a chainsaw needs to be protected from impacts to the head (from falling debris), the effect of sawdust and small particles flying towards the eye and from the noise of the chainsaw.
Protection can be provided by multiple components, each satisfying their own standard, or it can be delivered by a single product. There are different European standards that apply for each aspect of protection.
This article will look at three standards that could be combined to provide appropriate protection to the head. One option is for a worker to wear a combined system (that is, helmet/eye protection/hearing protection). The helmet should satisfy EN 397:2012+A1:2012 and will be fitted with eye protection that meets EN 166:2001, while the earmuffs should meet EN 352-3:2002. A second option is for the worker to wear a separate helmet, eyewear and earmuffs (EN 352-1:2002) or earplugs (EN 352-2:2002). There are other aspects to consider – such as chemical innocuousness and certification – which will generally also apply.
Other helmet standards
EN 397 is not the only option for Industrial helmets in Europe – there are additional standards for special cases. These circumstances include where higher voltages are expected (EN 50365:2002) or where additional protection is required (EN 14052:2012+A1:2012).
Other standards for industrial helmets exist outside Europe. The American ANSI Z89.1 evaluates flammability, force transmission and penetration. Helmets are classified according to where impact protection is provided and the level of electrical protection provided.
Industrial helmets are not the only type of helmet that may cover eye and ear protection. For many of these, the deceleration on a head form during a fall is measured.
EN 397 – resistance to impacts
The main helmet shell together with its harness provides protection to the top of the head. The typical industrial hard hat is a familiar sight on all building sites and is covered by EN 397:2012+A1:2012. An impact test is a mandatory and central requirement for such helmets. Other protection may be provided by the shell, and EN 397 includes additional tests covering the design and other safety-based requirements.
The impact test (figure 1) assesses the ability of the helmet to provide basic protection against moderate impacts that might occur on an industrial site, such as from a falling brick. This test is conducted by mounting the helmet onto a fixed head form and then impacting it with a vertical falling mass. The force experienced by the head form beneath is recorded with a maximum transmitted force of 5kN being permitted. An impact energy of approximately 50J is used, which is achieved by dropping a 5kg hemispherical striker onto the helmet from a height of one metre. These impacts are carried out on the crown of the test helmets after conditioning them to high and low temperatures, water immersion and artificial ageing (by exposing the helmets to an intense ultraviolet light). This helps to ensure that helmets remain protective during ‘reasonable’ use.
In addition to this protection from blunt objects, some protection must be provided against sharp objects. The test used to assess this characteristic utilises a falling 3kg striker with a conical point (figure 2). The shell must prevent the point of the striker making any contact with the head form.
EN 397 also includes a number of tests on helmets where optional protection is claimed. Helmets may be claimed to protect against extremes of temperatures, splashes of molten metal, electrical voltages up to 440V and deformation from lateral forces.
Helmets can only protect when they are retained on the head and if they fit properly.
For this reason, most specifications for protective helmets include a number of requirements for the design of a helmet, in addition to the specific performance requirements – such as those already mentioned.
There are a number of ergonomic and safety-based requirements, such as the clearance between the head and the shell of the helmet, and the width of the cradle. These ensure the helmet can be worn without causing inconvenience to the wearer.
The rear adjustment must permit adequate fit for any head in the stated size range. In addition, a chin-strap may be supplied. EN 397 requires that either the helmet shell or the headband is fitted with a chinstrap or the means of attaching one. The chinstrap should have a minimum width of 10mm, and the strength of the strap attachment should be sufficient to enable the chinstrap to hold the helmet on the head but not so great that the strap could become a strangulation hazard. To test this, the helmet is mounted onto a suitably-sized head form and the chinstrap is passed around an artificial jaw (figure 3). A tensile force is applied to the jaw at a rate of 20N/min until the jaw is released due to failure of the anchorages. The force at which this occurs should be no less than 150N and no more than 250N.
EN 352 – attenuation of noise
Prolonged exposure to high levels of noise can damage a person’s hearing. In the EU, for example, the level at which hearing protection must be made available is 80dB, and the employer must assess the risk to health. At 85dB, the wearing of hearing protection is mandatory. However, suitable protection – such as earmuffs – can attenuate louder noises to safer levels.
The relevant standards for hearing protection can be found in the EN 352 series. EN 352-3:2002 covers helmet-mounted earmuffs. If ear protection comprises separate ear muffs or earplugs, these would be covered by parts 1 and 2. These standards assess the passive protection - that is, the protection intrinsically provided by the protector’s construction. Parts 4 to 7 contain requirements and tests for active devices, and these take into account the behaviour of electronic circuitry. Such assessments are valuable for conditions where a combination of high level of protection, situational awareness and ease of communication is needed (for instance, when working near railway tracks).
A range of physical and mechanical tests are carried out to assess the ear protector’s basic performance. Initial testing begins with assessing if the product can fit on the claimed head size range, and whether or not it has appropriate adjustment. The headband force is measured, following which the hearing protectors are subjected to a drop test (or optionally, a ‘low temperature drop’ test), a flexing test, water immersion or an optional water immersion with the headband under stress. After this, the headband force is re-measured and the change in headband force is calculated.
Acoustic assessment of passive hearing protectors includes two basic tests – sound attenuation and insertion loss. These establish whether harmful levels of noise are reduced to acceptable levels at the ear.
The ‘insertion loss’ acoustic test (figure 4) is conducted by an electro-acoustic method. The test evaluates the levels of noise received by microphones placed in a fixture representing the head. This compares the levels of noise received, both with and without the hearing protector in place. The insertion loss test is carried out to ensure that the hearing protection proved by the set of samples assessed is at a consistent level.
While the passive devices considered can still provide different levels of protection at specific frequencies, active devices can use electronic circuits to provide additional effects. This helps in conditions were high levels of protection, easy communication and situational awareness are needed (for instance when engaging in railway work).
One option is to use speakers inside the earmuffs to relay external sounds, such as a conversation with a co-worker. When levels of sound are low, they are reproduced at an unattenuated form for the wearer, whereas high (damaging) levels of sound are not replicated at full amplitude. Another option is to use the circuit to produce the same sound, but with an opposite phase. These noise-cancelling systems provide additional protection.
In all cases, the general structure of the test is to use microphones near the ear and to determine at what levels of external sound the ear will be exposed to combined sound levels (from sound passing through the earmuff and from recreated sound) that approaches dangerous levels. Such an assessment is also used to ensure that internal speakers do not produce harmful levels of noise.
The sound attenuation test is a subjective assessment using human wearers and is carried out in a hemi-anechoic chamber (figure 5). The subjects indicate the threshold sound level – with and without the protectors. The difference (in dB) is the level of protection the protectors provide at the test frequency. If the protection is purely passive, in principle the protection provided is independent of volume. These values can be summarised into a representative attenuation for ‘high’, ‘medium’ and ‘low’ frequencies (the ‘HML’ ratings), or even further into a ‘simplified noise level reduction’ which provides a ‘single number rating’ (SNR).
Noise reduction rating
The American equivalent of the single noise rating is the Noise Reduction Rating (NRR). The equivalent standard ANSI S12.6 explicitly has two test procedures to reflect the differences between ‘individually trained and well-motivated users’, and the majority of users who cannot be described in this way.
EN 166 – eye protection
The key standard for eye protectors is EN 166:2001. This specifies minimum requirements for a range of performance tests. It covers all designs of eyewear, including separate eye protectors and those forming part of a combined PPE device. Where the eye protection being tested is a mesh visor, the applicable standard is EN 1731:2006.
EN 166 includes a range of optical performance requirements, the methods of assessment of which are specified in EN 167:2001. These apply to all lenses as testing is required to ensure that the eyewear does not have any harmful optical effects. One of these tests is a ‘field of vision’ assessment to ensure that nothing in the frame impedes vision.
Transmission tests measure the percentage of incident light which the lenses transmit to the wearer’s eyes. Where no filtering action is necessary, the levels must be greater than 74.4 per cent.
Any tendency for the eyewear to create a diffusing effect should be minimised. Refractive power tests involve viewing a target through a telescope, with and without the lens. The adjustments needed to keep the target in focus are directly related to the spherical and astigmatic powers of the lens. Prismatic powers are also assessed to ensure that the lenses do not unduly deflect the image.
EN 166 also includes assessment of mechanical properties, and the test methods are described in EN 168:2001. These include the increased robustness test which is conducted on all eyewear, including spectacles, goggles and visors, and the optional high-speed particle test (figure 6), which is carried out if the eyewear is claimed to offer high-speed particle protection. Other mandatory tests include establishing resistance to ignition (from a heated metal rod), corrosion and ultra-violet (UV) ageing.
In many cases, eyewear has to protect against optical hazards such as UV light, intense light sources or sun glare. These are covered by a separate range of standards which specify transmission requirements. There is a wide range of tests for optional physical performance claims. These include evaluations for protection from molten metals and hot solids, droplets and splashes of liquids, large dust particles, gas and fine dust particles, surface damage by fine particles and fogging.
Shielding the eyes
In many cases, eyewear must defend against optical hazards, such as UV light, intense light sources or sun glare. These are covered by a range of standards in addition to EN 166 which modify the transmission requirements, and add appropriate modifications and requirements – for instance, welding goggles are allowed higher levels of diffusion. The maximum transmittance is specified for certain parts of the visible and UV and infrared spectrum.
The effectiveness of the product will often be indicated by a scale number. This categorises the protection the lenses provide against UV and visible light. The filtration of visible light must not be harmful. If good colour recognition is required, the lenses should be tested to ensure that red, green, yellow and blue signal lights can be distinguished.
Innocuousness and certification
The materials used in such helmets are required to be innocuous and free from harmful substances. Textile parts in contact with the skin should be checked to ensure that their pH is generally neutral and that no banned azo dyes are present. Rubbers and polymers in contact with the skin should be tested to ensure that there are no Polycyclic aromatic hydrocarbons (PAHs). Metal components in contact with the skin should be free from nickel. Manufacturers which require an EU type-examination will need test data to prove the safety of such materials.
Under the EU PPE Regulation, most of the PPE discussed in this article will generally be ‘Category II’ – in other words, the product must be certified according to module B by a Notified Body such as SATRA before the CE mark can be applied and a declaration of conformity is completed. However, all hearing protection and any PPE protecting against certain hazards (such as high voltages) is ‘Category III’. For these products, the ongoing conformance monitoring must also be inspected by an appropriate Notified Body using either the module C2 or module D route.
By demonstrating that all requirements for the relevant standards are met, the components protecting the eyes, ears and head can be seen to be effective. This provides a strong basis for demonstrating compliance to the directive when certifying.
Testing and EU certification at SATRA
SATRA can test PPE against European, international and national standards and, as a Notified Body, can certify PPE for the CE Mark. There are two SATRA Notified Bodies – one in the UK and another in the Irish Republic, with a team of experts on hand to help customers through the process of the testing and type-examination according to the requirements of the PPE Regulation. SATRA is also able to carry out module C2 checks on samples from bulk production as specified in PPE Regulation or module D quality management system audits in the manufacturing facility.
SATRA is able to test and certify protective gloves, safety footwear, fall protection equipment, high visibility garments, hearing protection, and protective clothing (including items designed for motorcyclists). Products providing eye, face and head protection, PPE to be worn when engaging in sports or using a chainsaw, and items to protect against heat and flame can also be assessed in SATRA’s laboratories.
Other situations requiring this PPE
There are many other occasions where similar hazards may be faced. A welder on a noisy construction site will also need to protect his eyes from the arc equipment. While this adds additional requirements to EN 166 testing, the principles and standards are the same.
Military pilots and racing drivers still need to protect their head, eyes and ears, but an industrial helmet would not protect against the hazards they face. While EN 397 would not be a suitable standard, similar principles would apply – whichever helmet standard is used, while EN 352 and EN 166 would still be relevant.
Other families of standards
There are other families of standards with very similar ranges and test principles. International standards include the upcoming draft EN ISO 18526 test methods, as well as draft EN ISO 16321 (for occupational use) and EN ISO 12312-1:2013+A1:2015 (for sunglasses).
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