Protective footwear – requirements selection and ergonomics

Introduction

This article provides information for end-users of foot and leg protective wear, as well as for employers and OSH services providers. This article covers definitions, technical and protective requirements as well as provides a brief overview on the characteristics of selected footwear designed for use in special work environments (i.e. fireman’s shoes and protective footwear for chainsaw users). The ergonomic aspects and comfort of use related to characteristics of foot microclimates are also described. At the end of the article, there is a summary offering guidelines and general rules for properly selecting occupational, protective and safety footwear. In general, the footwear worn in the workplace should be chosen to avoid injuries caused by:

• contact with falling, rolling or cutting objects;
• penetration through soles or uppers (stepping on sharp and pointed elements);
• anti-static and electrical hazards;
• contact with chemicals and biological agents,
• exposure to thermal factors (cold and heat) as well as molten metals,
• wet and slippery surfaces.

Definitions

• Insole: Non-removable component used to form the base of the shoe to which the upper is usually attached.

• Insock: Removable or non-removable footwear component used to cover part or the entire insole. NOTE! “Non-removable" means that the insock cannot be removed without being damaged.

• Lining: Material covering the inner surface of the upper, the layer in direct contact with the wearer's foot.

• Cleat: Protruding part of the outer surface of the sole.

• Rigid outsole: Sole which cannot be bent at an angle of 45° under a load of 30 N, tested in accordance with ISO 20344^[1].

• Cellular outsole: Outsole which has a density of 0.9 g/ml or less with a cell structure that is visible under 10" magnification.

• Penetration-resistant insert: Footwear component placed in the sole in order to provide protection against mechanical penetration.

• Safety toecap: Built-in footwear component designed to protect the toes of the wearer from impacts of an energy level of at least 200 J and compression at a load of at least 15 kN.

• Seat region counter area: Rear 10 % of the total length of the footwear (upper and sole)

• Water penetration: In accordance with ISO 20344, water penetration is expressed as the mass increase of the absorbent cloth after 60 min^[1].

Figure 1: EN ISO 20345 describes elements of the footwear.

Classification of footwear

Footwear designed for foot and leg protection is classified under Personal Protective Equipment (PPE) and is covered by the following EU Legislation:

Directive 89/656/EEC^[3] lays down the minimum requirements for PPE used by workers at work.

Regulation 2016/425/EU of 9 March 2016 on personal protective equipment^[4] defines legal obligations ensuring that PPE on the European market gives the highest level of protection against hazards.

Personal protective equipment, including foot and leg protection, must be used when the risks cannot be eliminated, avoided or sufficiently limited by technical means of collective protection or administrative procedures within the organisation.

Regulation 2016/425/EU divides PPE into three categories based on the type of risks they address and lays down different conformity assessment procedures for each of these categories. Most types of protective footwear are Category II PPE. The conformity assessment procedures requires an EU Type Examination by a notified body. More information on the conformity assessment procedures can be found in the article on PPE.

There are three basic standards characterising requirements for footwear designed for foot and leg protection, i.e.

• EN ISO 20345^[2] – defines the requirements for safety footwear,

• EN ISO 20346^[5]– defines the requirements for protective footwear,

• EN ISO 20347^[6] – defines the requirements for occupational footwear.

All three types of safety, protective and occupational footwear are classified as:

• class I footwear made from leather and other materials, excluding all-rubber or all-polymeric footwear,

• class II all-rubber (i.e. entirely vulcanized) or all-polymeric (i.e. entirely moulded) footwear.

According to the definition, safety, protective and occupational footwear incorporates protective features to protect the wearer from injuries that could arise through accidents. The difference between individual types of footwear is related to the presence of a toecap and its protective properties assessed within the laboratory tests.

Safety footwear

Safety footwear is fitted with toecaps designed to ensure protection against impact when tested at an energy level of at least 200 J and against compression when tested at a compression load of at least 15 kN^[2] .

Protective footwear

Protective safety footwear is fitted with toecaps designed to ensure protection against impact when tested at an energy level of at least 100 J and against compression when tested at a compression load of at least 10 kN^[5] .

Occupational footwear

The occupational footwear does not include toecaps designed for protection against impact force and compression load. These types of footwear are designed for workplaces and activities where both hazards, such as impact and compression, to feet and toes were not identified during the risk assessments.

Special application footwear

Safety, protective and occupational footwear are the basic types of footwear designed for protection against various hazards. Some professions related to specific activities and hazards require modified types of footwear characterised in their dedicated standards (table 1).

Requirements

Protective parameters

The protective parameters for safety, protective and occupational footwear, confirmed by laboratory tests, takes into account, i.e.:

• Design of footwear including height of upper and seat region;
• Whole footwear including:
  • sole performance with regard to construction and upper-outsole bond strength (only for category I footwear),
  • toe protection mounted in safety and protective footwear,
  • leakproofness (only for category II footwear),
  • ergonomic features,
  • slip resistance.
• Upper including:
  • general characteristics, tear strength, tensile properties, water vapour permeability and coefficient, pH value and chromium VI content for classification I footwear,
  • thickness, tensile properties, flexing resistance and hydrolysis for category II footwear.
• Quarter and vamp lining including:
  • tear strength and abrasion resistance,
  • water vapour permeability and coefficient (only for category II footwear),
  • pH value and chromium VI content.
  • Insole/insock;
• Tongue including tear strength, pH value and chromium VI content (only if present for category I footwear);
• Outsole including design, tear strength, abrasion and flexing resistance, hydrolysis and interlayer bond strength.

Each type of safety, protective or occupational footwear should meet the requirements on slip resistance, and one of the three slip resistance codes should be added to the marking of the footwear. These codes refer to the related test method:

• SRA – slip resistance on ceramic tile floor with NaLS solution,

• SRB – slip resistance on steel floor with glycerine,

• SRC – slip resistance on both ceramic tile floor with NaLS and steel floor with glycerine.

Categories and performance levels of safety, protective or occupational footwear, with regard to basic and additional requirements defined in the related standards, are listed in table 2.

Table 2 Marking categories of safety, protective and occupational footwear

Source: EN ISO 20345^[14] , EN ISO 20346^[15], EN ISO 20347^[16]

Additional requirements for safety, protective and occupational footwear with the appropriate symbols for marking include:

• Requirements related to the whole footwear:

P - Penetration resistance (footwear with anti-penetration insert);

C - Conductive footwear;

A - Antistatic footwear (it should be noted, that antistatic footwear cannot guarantee dequate protection against related electric shock as it only introduces a resistance between foot and floor);

I - Electrically insulating footwear;

HI - Heat insulation (footwear with soles resistant to heat environment conditions);

CI - Cold insulation (footwear with soles resistant to cold environment conditions);

E - Energy absorption of seat region;

WR - Water resistance;

M - Metatarsal protection (requirement related only to safety and protective footwear);

AN - Ankle protection;

CR - Cut resistance.

• Requirements related to the upper:

WRU - Water penetration and absorption.

• Requirements related to the outsole:

HRO - Resistance to hot contact;

FO - Resistance to fuel oil.

Ergonomic properties and comfortable use

Materials for manufacturing components of safety, protective and occupational footwear

The most common upper material for Class I safety, protective and occupational footwear is natural cowhide leather: with full or corrected grain and split leather with artificial grain added (top grain split leather)^[17] . The whole uppers or their fragments in safety, protective and occupational footwear are also made of synthetic leather and textile materials. The most common lining materials used in Class I footwear include natural leather, split cowhide and nonwovens. The main lining materials for all-rubber and all-polymeric footwear are woven and knit fabrics^[18]. The basic materials for manufacturing soles of safety, protective and occupational footwear are synthetic ones, such as various types of rubber (butadiene, butadiene styrene, nitrile, chloroprene rubber), polyvinyl chloride, polyurethanes. Novel sole materials include thermoplastic polyurethanes (TPU). They are soft, elastic, rubber-like, and highly resistant to abrasion, bending, tearing and tension^[19][20]. Currently, the most common insole materials include: synthetic cellulose leather, recycled insole leathers and insole nonwovens. All-rubber footwear is made of vulcanised rubbers: natural, nitrile and chloroprene rubber. The materials for all-synthetic/plastic footwear include: polyvinyl chloride, polyvinyl chloride modified with nitrile rubber, polyurethane.

Protective footwear can have additional elements guaranteeing specific protective properties. Such elements include^[21][22]:

• Internal elements called toecaps, protecting the toes against impact and compression. The materials include steel, aluminium or appropriate plastics. Metal toecaps should be resistant to corrosion. Plastic ones should maintain the required resistance to impact after chemical (exposure to acids, lye, fuel oil) and thermal (high and low temperature) ageing. Toecaps in class I footwear should have an element covering their rear edges, made of e.g. polyurethane or latex foam, to avoid compression of the foot.
• Anti-penetration inserts are mounted in the soles. The inserts should have appropriate dimensions and should be resistant to repeated bending. Metallic inserts should be resistant to corrosion and non-metallic ones to chemical and thermal ageing.
• Metatarsal protections safeguard the upper part of the metatarsus (the middle part of the foot) against crushing or contusions due to objects falling down, or cuts inflicted by sharp edges. Their design enables permanent mounting on the external part of the upper. They should be made of an appropriate material (steel or plastic) and appropriately shaped to avoid impairment of normal movements of the foot. The construction should ensure uniform distribution of the force generated during potential impact over the sole, toes and as large of an area of the foot as possible. Metatarsal protections are the elements of safety and protective footwear.
• Ankle protections are the shock-absorbing elements, made of e.g. polyurethane or latex foam and in all-rubber shoes – of grooved rubber.
• Elements covering the metatarsus prevent sand or stones, or (in footwear for welders and steelworkers) sparks and molten metal splashes, from getting inside the shoe of e.g. heat-resistant leather.

Testing and methods of assessing the ergonomic properties of safety, protective and occupational footwear

Ergonomic features : While selecting protective footwear, an optimal protection in respect of ergonomic features should be taken into account. Over-protection should be avoided. Ergonomic features of the footwear such as, for example, mass, rigidity of soling, and water-vapour permeability should be considered. The characteristics of ergonomic footwear include the appropriate shape and size, specific properties of the materials and ensuring adequate exchange of heat between the foot and the environment . Wearing comfort depends, to a considerable extent, on the individual adaptation of the shoe to the foot; for this reason, a shoe that properly fits should be chosen. Among others, the following influencing factors should be taken into consideration^[19]:

• The used lasts can differ from manufacturer to manufacturer but also within the collection of a manufacturer;
• If pressure is exerted on the foot by the toecaps, this can often be easily remedied by changing to a different shoe model;
• The padded collar with integrated ankle protection helps to avoid pressure points in the leg and ankle areas;
• Padding of the tongue helps to avoid pressure points on the upper part of the foot;
• Antimicrobial provision helps to avoid athlete’s foot developing due to foot perspiration;
• Air-condition membrane is especially important for shoes with high uppers, it optimizes the water-vapour diffusion and thereby reduces the formation of perspiration in the shoes;
• Consistent foot hygiene, which includes a daily change of socks and if possible a daily change of shoes if the wearer suffers from an increased level of foot perspiration;
• Class I footwear adapts to the users’ feet, it is not recommended to wear class I or II footwear that has already been used by other people.

Meeting the criteria of ergonomics by personal protective equipment is one of the essential requirements of Regulation 2016/425/EU. It makes the manufacturers responsible for ensuring the safety, health, hygienic and ergonomic properties of their protective products^[15][20] . The EN ISO 20344 standard concerns testing and assessment of safety, protective and occupational footwear. In addition, this standard also includes the methodology of testing and assessment of the comfort of use of footwear during usual work-related activities^[1] . The section concerning assessment of ergonomic properties in footwear contains the testing methodology and a questionnaire for the participants of the tests. This questionnaire included “Yes" or “No" answers concerning the condition of footwear surfaces, the adjustability of buckles/fasteners and difficulties caused by the footwear during marching with specific speed (4-5 km/h for 5 min), going up and down the stairs (17 ± 3) steps per max. 1 minute, kneeling and squatting.

There are also non-standardised methods for measuring the microclimate inside the footwear at worksites or under laboratory conditions (with specific workload imposed on the user under constant temperature and humidity conditions). These tests performed directly at worksites are difficult from the organisational point of view, because they require involving a cohort of test subjects for statistical reliability. Therefore since the 1980s, assessing the comfort of footwear use have utilised an artificial foot model. Such a method of testing is more objective and less complicated to organise. It enables to conduct a wide spectrum of tests under different conditions of usage and with many variants of footwear construction. It provides an alternative for utility tests carried out at worksites or under simulated laboratory conditions^[21][22] .

Selection

Selection of footwear designed for protection of feet and legs should be preceded by a risk assessment which includes:

• Identification of all possible risk factors occurring in the workplace,
• Characteristics of exposure of workers to harmful factors, e.g. :

- weight of the item, which can fall down or crash on the foot,

- type, concentration and physical state of a chemical (acids, bases, solvents, etc.),

- ambient conditions, temperature and humidity.

• Working conditions, e.g.:

- work in a standing position,

- activities involving constant movement,

- walking on ladders and stairs,

- movement on smooth and slippery surfaces,

- work in difficult field conditions,

- working in an open space (outdoor activities),

- work in confined spaces with constant temperature.

Selection of appropriate footwear for hazardous work tasks

Safety, protective or occupational footwear is designed to protect feet against a wide variety of injuries. Impact, compression, and puncture are the most common mechanical types of foot injury. The toe cups are commonly used as the ultimate protection from falling or rolling objects, as well as compression forces affecting the foot at work. Steel toe protection is the most popular and trusted forms of certified footwear, whereas lighter non-metallic toe cups are available on the market. Moreover, the non-metallic toe cup is not electrically conductive, and the resistance to the transmission of heat or cold can make a big difference on the job site.

To avoid foot injuries caused by treading on sharp or pointed elements, the footwear equipped in penetration-resistant midsoles should be selected. It is realised by application of non-removable inserts in the footwear.

Slips, trips and falls related to walking on slippery surfaces resulting in injuries such as fractured bones or sprained ankles could be reduced by selecting slip-resistant soles. The choice of the tread is a crucial aspect. Flexible footwear, which allows most of the tread elements to contact the walking surface, and those with the most tread elements per unit area of sole, are preferred. The tread should be smooth and flat on the contact surface and must not wear out quickly. Where there is water and lubricants, square or short rectangular tread designs have very good anti-slip characteristics.

Working in a cold environment requires footwear with thermal insulation, whereas work in hot conditions requires footwear with heat resistant and insulating soles. For protection against molten metal splash, footwear must have quick release fastenings.

Protection of feet or legs against chemical factors is realised by footwear that is impermeable and resistant to those chemicals. If the wearer has contact with organic solvents, fuel resistant outsoles are recommended. The characteristics of the chemicals determine the material that the footwear is made of. The most typical materials applied in footwear designed for protection against chemical risks are natural rubber, neoprene and polyvinyl chloride^[19] . For example natural rubber resists bases, acids, alcohols, and most water soluble chemicals. It is a flexible material that stays supple in cold weather, but is not recommended against oil based chemicals and solvents. The neoprene is resistant to most animal fats, blood, oils, alcohol, alkalies and caustics, whereas it reveals significantly lower puncture or cut resistance in comparison to natural rubber footwear. With regard to polyvinyl chloride it is characterised by good protection against animal fats, bases, alkalies, oils, many acids, alcohol and petroleum hydrocarbons. It is not recommended for use with most solvents, ketones and aldehydes.

With regard to risks of electricity, three general types of footwear are available, i.e. antistatic, conductive and electrically insulating footwear. All three types have very distinct purposes. This footwear should be selected in accordance with other types of personal protective equipment (protective clothing, helmets or gloves) fulfilling electrical requirements.

In case of workers operating in environments sensitive to static electricity, antistatic footwear should be selected, particularly in potentially explosive atmospheres or for the handling of sensitive materials. These types of footwear help to dissipate the accumulation of static electricity from the body while still providing a reasonable level of resistance to electrical hazards from live circuits. It should be noted that antistatic footwear cannot guarantee adequate protection against electric shock as it only introduces a resistance between foot and floor.

To protect the wearer in an environment where the accumulation of static electricity on the body is recognized as a hazard, conductive footwear should be selected. These workplaces are related to handling explosive or volatile materials. Conductive footwear is made with materials that offer no electrical resistance. The footwear dissipates static electricity from the body to the ground to reduce the possibility of ignition from a static electric spark, volatile chemicals, explosives, or explosive dusts. It should be noted that these type of footwear do not guarantee protection against live charges or electrical equipment. Electrically conductive footwear should not be used if the risk of shock from any electrical apparatus or live parts has not been completely eliminated.

Working conditions related to activities in low voltage installations require electrically insulating footwear. This type of footwear is used for working live or close to live parts on installations not exceeding 1 kV a.c.^[12] . The footwear, when used in conjunction with other electrically insulating protective equipment such as gloves or blankets, prevents dangerous currents from passing through persons via their feet.

Choosing the appropriate safety, protective or occupational footwear for the specific demands of work is essential to ensure that the footwear provides adequate protection. It should be pointed out that the selection of the appropriate footwear should be integrated with a monitoring procedure that ensures the footwear is serviceable prior to use. It also should be pointed out that the protective properties of the footwear are confirmed within laboratory tests for new items, therefore, end of service life and damage through use of the footwear should be taken into account.