HIGH-VISIBILTY

Definition:

High-visibility clothing is any clothing worn that has highly reflective properties or a color that is easily discernable from any background. Orange hunting vests are a popular example of high-visibility clothing.

In other words, High visibility clothing in good condition is important to alert motorists that there are workers on, or near, the road. It assists to create a safer workplace for employees.

Ø What types are there?

AS 4602, High Visibility Safety Garments, notes three different classifications for garments.

A short description of each classification, with some indicative illustrations -

A. Class D:

· Outdoor daytime use only.

· Fluorescent or other non retro-reflective1 high visibility material.

B. Class N:

· Night time use only.

· Retro-reflective material on a ‘non-specified’ background.

C. Class D/N:

· Day or night use.

· Combination of fluorescent and retro-reflective material.

· Where retro-reflective strips are applied to a garment, they should be 50 mm wide (not 25 mm).

Ø What type should be using?

There are many different products available, including clothing with high visibility panels, safety vests, and overalls / jump suits.

Environmental factors may include:

Ø Temperature (heat / cold)

Ø Lighting and visibility (day / night / artificial / twilight / rain / fog)

Task factors may include ensuring that:

Ø A non-flammable garment is worn whilst completing hot works.

Ø Works being undertaken near rail lines meet the specific requirements for this application.

Ø It is also important to remember to check that the vest being worn does not blend in with background colours.

The importance of Hi Visibility Clothing in some workplaces

There are certain workplaces that have very many hazards and employees are required to wear high visibility clothing to ensure that they remain safe. In workplaces such as construction sites, transport companies, warehouses, factories and roadwork, it is crucial to wear hi visibility clothing for your own safety. The hi visibility clothing will prevent employees from getting cuts, chemical and biological hazards, static electricity and high voltages.

The clothing is more visible during the night and for daytime work, the bright clothing can be worn on the main body. The high visibility clothing also protects employees in situations when it too hot. The material used prevents the heat from outside from affecting the body.

There are many employees who are killed each year while some are seriously injured at work especially in vehicle related incidents. The most common are situations where a pedestrian is struck by a forklift or a lorry that is reversing. In this cases, the driver does not see the person if they are not wearing any high visibility clothing.

The use of high visibility clothing greatly improves the visibility of the people in a workplace which reduces the risks of accidents and improves safety. There are laws that are in place to ensure that the employers ensure the safety and health of their employees is well taken care of. The high visibility garments are provided by employers and if the employees do not use them they are liable for prosecution if n accident occurs.

There high visibility clothing includes vests, t-shirts, trousers, jackets, hats and coveralls. The type of clothing that is used in a workplace will be determined by the ambience and lighting that is available in the area and conditions such as fog and snow.

There are jobs that will only require you to wear a waistcoat but some require full body high visibility clothing. If you are a maintenance worker or work in an area that has many moving vehicles, it is advisable to get the full body ones. This ensures that you are visible as possible to the driver.

Some occupations involve workers being out in very adverse weather and the high visibility clothing ensures that the workers are well protected from these conditions. Workplaces that are very dark are a potential hazard and hi visibility clothing is necessary. The amount of clothing that the worker puts on will also be determined by the lighting situation. Traffic police and civil engineers work in environments that are full of vehicles and this increases the risk of accidents. They should wear high visibility clothing to ensure that the drivers can spot them from a distance to avoid any accidents. This is very important if it is on a foggy day or its snowing.

There are various standards that are used to determine which hi visibility clothing is suitable for a specific workplace. Workers should use the right type to ensure that they are well protected from the hazards that are presented in their workplaces.

Safety Jackets

Most of the safety jackets have a reflective strip that reflects light in conditions of low visibility. These jackets are however of no use in habitats where there is no incident light, for example a mine or a dark street or railway track, as shown in Fig 1.

To overcome this shortcoming of the reflective type of jackets, we have developed a photo-luminescent fabric. Strips of this fabric can be cut and stitched on jackets along with the reflective strips so that these become visible during night under very poor visibility conditions in the absence of an incident light as shown in Fig 2.

Fluorescence, Phosphorescence and Glow in the Dark pigments:

When an electron absorbs light energy, it is usually excited to a higher energy level in the first excited state S1 as shown in Fig 3, before rapidly relaxing to the lowest energy level. This event is termed vibration relaxation or internal conversion and occurs in about a picoseconds or less. The decay straight from the S1 state to the So state after the internal conversion is termed as fluorescence. Phosphorescence decay is similar to fluorescence, except that the electron undergoes a spin conversion into a triplet state T1 instead of the lowest singlet excited state So' a process known as intersystem crossing. The stability of the first triplet excited state T1 is what determines whether a material is fluorescent or phosphorescent. Fluorescence occurs if this excited state is relatively unstable and phosphorescence occurs if it is relatively stable. This however is an inherent property of the material and cannot be changed. Thus phosphorescence is a much slower process than fluorescence.

Fig 3: Jablonski diagram to differentiate between fluorescence and phosphorescence

Glow in the Dark pigments usually contain two types of components; one being the fluorescent dye and the other the phosphorescent compound. What happens is that the phosphorescent material absorbs light and emits it slowly as a pale blue light. Then the pale blue light is absorbed by the fluorescent dye and emitted as a green or red light depending on the dye used. The most commonly used phosphorescent material is zinc sulfide mixed with copper. The green fluorescent dye is mostly sodium fluorescein and the red fluorescent dye is a Rhodamine. Since fluorescence is a much faster process than phosphorescence, the phosphorescent material forms the source and the fluorescence material takes up the role of the device for energy consumption (Fig 4).

Fig 4: Chemical structure of fluorescent dyes present in glow in the dark pigments

Sodium fluorescein Rhodamine B

High visibility clothing for construction side

All railway tracks require maintenance. It is rare for a rail service to be suspended during routine jobs, which means people have to work in close proximity to busy lines, albeit with train speed restrictions implemented in areas subject to working. To increase the visibility or conspicuity of workers, a number of actions can be taken. Warning lamps and signalling devices may indicate work activity. However, these do not indicate the location of individual workers. To achieve this, personal protective equipment (PPE) is required.

On the UK railway network the wearing of high visibility clothing has become a mandatory requirement for all persons associated with track or lineside working.

Railway workers may find themselves carrying out maintenance work on track, where no trains are running – called 'Green Zone working'. However, much work is undertaken on active railways, during day and night, and under different weather conditions. Under such circumstances, known as 'Red Zone working', the dangers are real and ever present and it is important that the highest levels of visibility are maintained.

The main feature of high visibility clothing is that it is made from materials that aid conspicuity by day and night. To enhance the visibility of a wearer during the day, garments are made from fluorescent materials of standard colours. The visibility of a person is aided at night by the inclusion of retroreflective tapes within the construction of a garment. Retroreflective materials reflect a high proportion of light back towards it’s point of origin.

There is a large range of high visibility clothing available. However, there is a particular specification for clothing that is allowed to be worn on the UK rail network. The specification is set out in Railway Group Standard GO/RT 3279:2008, a document that defines the ‘minimum requirements for high visibility clothing for being conspicuous on the lineside or on or near the line’. The document also sets out special requirements for the high visibility clothing of Rail Incident Officers, who may be on a track following accidents.

High visibility Clothing

Being highly visible under both day and night-time conditions is an essential requirement in many situations. While the hazards may be common to many professions, the working environments where high-visibility garments are worn are extremely varied. This is represented in the different designs of high-visibility clothing currently available, ranging from vests used by warehouse operatives to water-resistant jackets and trousers worn by highway maintenance workers or railway engineers.

It is important that the materials and garment types are suitable for the environmental conditions that will be experienced in wear. In Europe, the standard EN 471:2003 high-visibility warning clothing takes this into account by providing not only a range of design requirements but also minimum requirements for the various materials and fabrics used in the garment’s construction.

EN 471 defines fabrics that have inherently high daylight visibility as ‘background material’ and other material, generally in the form of tape with night-time reflective properties, as ‘retroreflective material’. Other non–European standards allow for the manufacture of products for daylight use or night-time use but, in practice, most garments are designed for both. There are also ‘combined performance’ materials. Rather than using two different materials to provide night-time and daytime high-visibility, a single material is used that is highly visible during the day and also highly reflective during the night.

Breaking down EN 471

Broadly speaking, EN 471 can be split into three distinct sections as described below.

· EN 471 clause 4 – garment design

EN471 addresses a number of design criteria such as the minimum visible area of the various material types and the positioning and minimum width of the retroreflective material.

· EN 471 clause 5 – background material

The background material consists of coloured fluorescent fabric intended to be highly conspicuous during daylight conditions (fluorescent materials give off light when light is shone onto them). EN 471 details three specific colour requirements – ‘yellow’, ‘orange-red’ and ‘red’. These are defined by colour ‘coordinates’ measured using a spectrophotometer both before and after a treatment intended to assess the durability of the material to fading when exposed to sunlight. Other treatments include colour fastness to rubbing and perspiration, washing, hot pressing and bleaching. In addition to colour measurement, EN 471 includes tests for the strength of the fabric, resistance to water ingress (a hydrostatic head test) and its breathability (an important property that influences garment comfort) using a skin model test apparatus.

· EN 471 clause 6 – retroreflective material

Night-time or low light level visibility is achieved using retroreflective material, which ‘bounces’ light from discrete light sources (e.g. vehicle headlights) directly back to the source. Testing is carried out at a range of incident angles on both new material and material which has been subjected to various pretreatments, such as abrasion, flexing, folding at cold temperature, exposure to extreme temperature variation, washing and/or dry cleaning and simulated rainfall.

· Certification

In Europe high-visibility garments are considered to be personal protective equipment (PPE) and subject to the requirements of the European PPE Directive. Manufacturers need to work with a Notified Body, such as SATRA, to have an example of their garments type approved and associated documentation assessed, prior to the issue of an EC type approval certificate.

In Plant study of High Visibility fabric

Above fabric specification :

Weave : Satin ( to improve reflection )

Fabric P/C blends composition:

1. Polyester = In Warp wise

2. Cotton = In Weft wise

· Polyester fiber dyed with Fluorescent Disperse Dyes.

· Cotton dyed with reactive / vat dyes.

Process Route

Grey Issue

Singing + Desizing (Enzymatic)

Heat setting for polyester

Scouring + Bleaching

Mercerization

Souring

Dyeing

Finishing (Normal + Sanfo.)

Physical and chemical Test (after finishing)

Inspection and Packing

Dying Process Route:

Special type of luminous Disperse dyes (Fluorescent dyes) are taken in a and P/C blend fabric is padded together with 30% to 40% squeezing expression.

After this the fabric is dried. At this time Disperse dyed are fixed in the polyester.

After this the fabric is send on CDR (Continues Dyeing range) machine. At this time the fabric is padded with vat dyes (With Hydro + NaOH) in soluble form. The cotton is dyed with Vat dyes.

After Dyeing is over the fabric is oxidized to convert vat dyes in original insoluble form by Hydrogen Peroxide (H2O2).

After this the fabrics is washed and send for finishing.

Generally normal finish is applied.

· Fabric then sends for Physical and chemical testing.

Physical Test:

Ø Tearing strength

Ø Tensile strength

Ø Seam slippage strength

Ø Abrasion

Ø Cover Factor

Ø Pilling

Ø GSM

Ø EPI x PPI

Ø Warp x Weft (Count)

Chemical Test:

Ø Washing Fastness

Ø Water Fastness

Ø Perspiration Fastness ( Acid + Alkali)

Ø Sublime Fastness

Detail on dying process route

New high visibility Nomex ProVis solution for industrial workers:

There is an increasing demand from industrial workers and contractors operating in high risk areas to wear an EN471 (high visibility) compliant garment that has the additional benefits of heat and flame protection.

Using the world renowned Nomex fibre, DuPont Personal Protection has developed a yellow high visibility solution called Nomex ProVis: this solution offers inherent protection from heat and flame, from molten metal splashes, and from heat of an electric arc; it is anti-static and performs in environments where high day light visibility is required.

Nomex ProVis is based on an engineered blend solution manufactured with a DuPont proprietary spinning technology. The special construction of Nomex ProVis fabric provides equivalent thermal and physical properties to Nomex Comfort fabrics, in combination with the additional requirements for EN471 high visibility yellow.

Oriol Rofes, Nomex Marketing Manager, explains: “We identified a need for very comfortable flame resistant protective clothing that also offered high visibility and so we developed Nomex ProVis. Whilst the garment offers much needed high visibility it also incorporates Nomex, a recognized flame resistant fibre from DuPont. Nomex ProVis offers protection against a multitude of hazards for employees working in many different industries such as petrochemical and utilities.”