The issue of an EU type examination certificate shows that the approving Notified Body is satisfied that an article of clothing meets the basic health and safety requirements of the Regulation. The route by which it is demonstrated that a garment meets the requirements is to test it in accordance with the requirements setout in an EU harmonised standard, in this instance EN ISO 20471.
A three-class system
The design requirements set out in the standard EN ISO 20471 classify garments according to the minimum amounts of high-visibility materials “EN ISO 20471 permits the use of three colours as background material: fluorescent yellow, fluorescent orange-red or fluorescent red – these colours are specified in terms of their chromaticity co-ordinates and luminance” that can be seen in the finished garment. This three-class system has Class 3 garments providing the highest level of conspicuity.
The standard permits Class 3 to be met by having a single garment or an ensemble – for instance, a classified jacket and a classified pair of trousers. Where an ensemble is specified, this will be deemed to meet the requirements of the standard only when the supplier provides clear instructions on how the classification has been achieved. A Class 3 garment is required to cover the torso and have sleeves with reflective bands or/ and trouser legs with reflective bands.
The standard demands uniformity in the design of high-visibility garments. This is because the conspicuity of a garment wearer is dictated as much by the design of a garment as the distribution and placement of visibility materials within it. The specific design requirements for garments are defined according to the general design of a garment, with types being defined as follows:
Garments covering only the torso – for example, vests and tabards
Garments covering the torso and arms – such as jackets, shirts, coats and t-shirts
Garments covering the legs – for instance, waistband and bib and brace trousers, and shorts
Garments covering the torso and legs – including coveralls without sleeves
Garments covering the torso, arms and legs – for example, coveralls with sleeves
All high-visibility garments are required to have fluorescent background material incorporated into their construction. Background materials, which provide day-time conspicuity, must meet particular colour definitions that are given in the standard.
“measurement is undertaken on a specialist piece of equipment known as a gonio-photometer system”
EN ISO 20471 permits the use of three colours: fluorescent yellow, fluorescent orange-red or fluorescent red as background material. These colours are specified in terms of their chromaticity co-ordinates and luminance, which is measured using a defined type of spectrophotometer under specific conditions.
The night-time conspicuity of a high-visibility garment wearer is maintained by having an arrangement of tape materials laid over the top of a background material. The tapes are made from materials which have a specific property of retro-reflection.
Retro-reflective materials have the property of returning a cone of light back towards the source from which it came. It follows then that for a garment tape to be visible it must have light falling onto it and an observer of the illuminated surface must be within the cone of retroreflected light in order to see its full effect.
This situation occurs when the driver of a vehicle equipped with headlights sees a pedestrian that is illuminated by the light of their car. A driver sitting more or less behind the headlights of the vehicle will also be within a cone of retro-reflection, providing a garment tape produces an effective cone of light. The laboratory measurement of retro-reflective materials is undertaken to define the specific retro-reflection within the cone of light formed by a material. Measurement is undertaken on a specialist piece of equipment known as a gonio-photometer system.
Manufacturing a garment tape that has a retro-reflective surface is usually achieved by one of two means. The most commonly used type is one that uses bead technology.
Microscopic bead technology
Microscopic glass beads of different diameters are distributed over the surface of a substrate layer, which is usually, but not exclusively, a textile material. These beads are stuck to the substrate by a silvered adhesive layer which forms a mirror around the part of the bead that is embedded. The performance of the tape is determined by several factors, including glass bead sizes, their spherical state, or rather lack of it, their distribution over the surface of a substrate layer, and the depth to which they are embedded in the adhesive layer.
A scanning electron microscope image showing the mixture of glass beads that makes up the surface of a retro-reflective tape
The durability of a tape depends not only upon how well individual beads are held in position on the tape, but also the flexibility of the adhesive layer and the inherent strength of the substrate material. Any loss of beads leads to a reduction in the retro-reflective performance of a tape.factors, including glass bead sizes, their spherical state, or rather lack of it, their distribution over the surface of a substrate layer, and the depth to which they are embedded in the adhesive layer. The durability of a tape depends not only upon how well individual beads are held in position on the tape, but also the flexibility of the adhesive layer and the inherent strength of the substrate material. Any loss of beads leads to a reduction in the retro-reflective performance of a tape.
Another type of retro-reflective tape that is used in the construction of high-visibility garments are those based on micro-prismatic structures. This type of material is embossed with many retro-reflectors that are shaped liked the corners of a cube.
As the arrangement of a microprismatic surfaces is made from an engineered surface, micro-prisms can be arranged in different orientations to provide different paths of retroreflection. Each micro-prismatic shape functions by reflecting light from the three sides of its structure. The geometry of these micro-prisms is such that light is reflected back towards its source. The collective effect of the many micro-prisms embossed on a tape provides the required level of retro-reflection.
The geometrically-shaped embossed surface of a micro-prismatic tape as revealed by a scanning electron microscope
The standard EN ISO 20471 specifies minimum levels of retro-reflective performance for different types of tape that may be used in garment construction. These are tapes made from materials that are defined as retro-reflective separate performance material (tapes intended to exhibit retro-reflective properties only) or combined performance material (tapes that have the properties defined colour properties of background materials and also retro-reflective properties). Therefore, manufacturers should always make sure that the retro-reflective material they intend to use meets their market’s demands.
Products produced to comply with EN ISO 20471 will be used under a variety of conditions, ranging from being worn by a patrolling car park attendant to a person working under very dirty conditions in an activity such as road maintenance. However, used garments will become soiled during their use. This will require them to be laundered or dry cleaned. In order for a highvisibility garment to remain effective it must be capable of withstanding the rigours of cleaning, both in terms of maintaining its integrity, that is without suffering seam breakdown or malfunction, and the performance of its high-visibility components.
Testing of a garment includes laundering of background materials and tapes prior to colour or retro-reflectivity measurement. Measurements are made to determine that a material can maintain minimum levels of performance in wear. In order to demonstrate the compliance of the cleaned product the performance of the background material and the tape are assessed after being laundered to the maximum number of wash cycles intended for a garment.
“high-visibility garments need to be constructed to a set of regulated design requirements that do not compromise the safety of the end user”
High-visibility garments can be manufactured from different types of materials, warp or weft knitted materials or woven fabrics. These materials must be sufficiently robust to withstand the rigours of their use; therefore, they may be tested for their physical strength, by burst, tensile or tear strength, as appropriate. The design of a garment influences conspicuity, so a garment must meet laid down design criteria. A garment must be classified to one of the three classes that are permitted. This is of particular importance when supplying garments for use in different risk environments.
It should also be of note that some organisations mandatorily require certain classes of garments to be used in certain situations. As examples, in the UK class 3 garments are specified by the highways agency for use on high speed roads, whilst a certain colouration of garments is required on the rail network.
Garments are also examined to see if they are ergonomically sound. Other tests include colour fastness to ensure the garment fabric is able to withstand the effects of sunlight by exposing it to a Xenon arc lamp. The PPE Regulation demands that materials used in PPE clothing are not harmful to a wearer. Therefore, a certain amount of chemical testing is required of high-visibility materials. Tests are usually conducted to determine whether substances that are prohibited from use are present, or whether substances that are present are there in limited amounts.
Therefore, to ensure that the end-user has the highest level of protection possible, high-visibility garments not only need to be assessed for physical properties, physiological properties, and health and hygiene issues, but also need to be constructed to a set of regulated design requirements that do not compromise the safety of the end user.