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Work clothing
International Journal of Industrial Ergonomics, 7 (1991) 77-85
77
Elsevier Guidelines
Work clothing R u t h Nielsen Laboratory of Heating & Air Conditioning, Technical University o/Denmark, 2800 Lyngby, Denmark
(Received February 5, 1990; accepted February 7, 1990)
1. Identification More than half of the working population uses work clothing of some sort. Work clothing has a shorter lifespan than other ergonomic investments in the work environment and there are therefore good possibilities to change to the best qualities available when new purchases are done. Economic studies have shown that the price of the work garment itself is not the major cost for a company in supplying work clothing to its employees. The basic function of work clothing is to keep the body comfortable with a pleasant thermal micro-climate close to the body, and at the same time to protect the body against injuries, external factors and contact with dirt, dust, chemicals, oil, rain, etc. Depending on whether the requirements to protection, appearance or comfort are dominating the clothing worn is called protective clothing or work clothing. The borders between these two groups are not strict. Ear and eye protection, protective helmets and respiratory masks, security shoes and safety belt with line are examples of protection. Also, clothing to protect against extreme heat and cold or dangerous substances is protective equipment. Work clothing is clothing that should be worn all day, which means clothes that are used in normal (and not extreme) situations. Traditionally, work clothing has also been used to give group identity and to show group membership. Some workers wear uniform, service dress, etc., others use work clothing of a more normal type, and then we find several small groups using very specialized work clothing. However, work clothing does not or should not only include the outer clothing layer we see. It comprises all the 0169-1936/91/$03.50 © 1991 - ElsevierScience Publishers B.V.
different layers in a clothing ensemble worn, and also footwear, hand wear, and head wear.
2. Requirements/function 2.1. General
The requirements to work garments are determined by the interaction between man, clothing and environment. To have an overall good function, the clothing ensemble must have several different qualities (figure 1). Because of the thermal properties of clothing and the interaction with human heat exchange, non-compatible requirements to both material and composition of the clothing often result. Today, many of the protective requirements to the environment can be met; however, the problem is to do it while keeping thermal comfort. Therefore, a work clothing ensemble is often the result of a number of priorities and compromises between requirements to thermal comfort, mobility and different types of protection.
i ON°R,
PROPERTIES
[ TEAR& WEAR] PROPERT'ES I
( ~L~T.,.n ~-.---I COMFORT I PROTECTION PROPERETSI ~
' PROPERTIES I \1 APPEARANCE
Fig. l. Properties ofimponanceforthefuncfionofclothing.
78
R. Nielsen / Work clothing
To dress correctly in a not too hot environment at a low activity is no problem. It is just to dress until not freezing. Problems develop when man in periods performs hard physical work and must get rid of extra heat and sweat, and at the same time must have protection to environmental factors. Here, a few facts on human thermoregulation and heat transport in clothing may be necessary. During physical work, almost all the energy will eventually be converted into heat. During hard industrial work the average heat production of man is often increased 4 - 5 times over the resting value of 60 W / m 2. Some of this heat is used to regulate the body temperature at 37-38°C, the rest should be dissipated to the environment. Whenever the temperature in the environment is lower than skin temperature heat can be given off as a dry heat flow by radiation, convection and conduction through the clothing or directly to the environment from uncovered body areas. When this route of heat dissipation is not sufficient to keep up with heat production, body temperature begins to increase, and sweating will start. Evaporation of
the produced sweat from the skin will take place whenever the relative humidity in the vicinity of the skin is less than 100%. Evaporation of 100 g sweat dissipates 245 k J, so evaporation of sweat is an effective avenue for heat dissipation. If evaporation is restricted (for example by impermeable clothing), the body temperature will increase over its regulated level, and eventually reach levels where heat exhaustion and heat stroke may occur. In warm environments heat may be transmitted from the environment to the skin by radiation, convection or conduction. Thermally, clothing is mainly characterized by resistances to dry and wet heat loss. Each fabric layer is characterized by the two resistances. The resistance to dry heat loss ( - i n s u l a t i o n ) is proportional to the thickness of the fabric layer, whereas for water vapor permeability the construction of the fabric layer is also important. Both for the insulation and the water vapor permeability the thickness of the enclosed air layers in an ensemble is of major importance. Insulation is increased more by a non-moving air layer than
GARMENT
FUNCTION
Underwear Socks (Hat) (Gloves)
Protects and/or ventilates the micro-climate near the skin. Regulates the dissipation of heat and humidity. Important for sensation
Shirt Blouse Sweater atc
Increases heat insulation by creating a non-moving air layer. May absorb end distribute the humidity, ~ may also limit heal dissipation.
Jacket Trousers Vest Skirt Overall
Protects against the environment
,tiv__ee Suit Rain suit Winter coat
Gives an Increased protection against external factor as rain, cold, wind, and hazardous agents.
(Hat) (Gloves)
Fig. 2. A layeredclothing system and the function of each layer.
R. Nielsen / Work clothing
by a textile layer. The vapor permeability is generally more dependent on the fabrics, but it will decrease with increasing thickness of air layers. When man exercises, the air enclosed within the clothing moves, the thermal gradients are disturbed, and air will by forced convective movements be exchanged through openings and directly through fabric layers with air in the environment. This air exchange may amount to more than 100 1/min and it reduces the insulation and increases the vapor permeability of the clothing ensemble considerably. The final exchange is dependent on activity level and pattern, and on the size of the openings. Wind and movements will decrease the insulating air layer sticking to the outside of the clothing, and with an open structure in the outer layer or with large openings wind will penetrate into the clothing, thus increasing heat loss. High air velocities may compress the clothing and thus reduce its insulation because the enclosed air layers are reduced. If clothing gets soaking wet from sweat or water, its insulation decreases. The heat dissipation by evaporation from wet clothing can be considerable, especially when the air velocity is high. However, as this evaporation does not cool the skin directly - only by an increased dry heat loss - it is not so effective. A clothing ensemble should be considered as a multi-layered clothing system comprising an inner layer (underwear), middle layers (e.g., shirt, sweater), and an outer shell layer (e,g., wind breaker, rain gear) (figure 2). Some of the layers may be superfluous in a warm environment, but when all are present in cooler environments each layer serves a specific main purpose. In addition to its hygiene function, the underwear is important for the direct cooling of the skin, for absorbing sweat, and thus, for our sensation of the micro-environment at the skin. The middle layer mainly serves insulating purposes, and the outer layer serve as a protection to environmental factors or as a practical layer for storage of tools etc. A clothing ensemble that should function with high requirements to protection and comfort must be put together methodically from the inside out.
2.2. Comfort properties Comfort in a physical sense means that the body is in a heat balance with the environment
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(thermal comfort), that the body is not subject to pressure from narrow or badly designed clothing (movement comfort), and that skin irritation does not occur from unpleasant contact with the clothing (sensorial comfort).
2.2.1. Thermal comfort Thermal comfort is defined as that condition of mind which expresses satisfaction with the thermal environment. In dressed man this will mostly be determined by the thermal micro-climate at the skin, which results from the thermal function of the clothing worn. The thermal c o m f o r t / d i s c o m f o r t experienced with a clothing ensemble is not only dependent on the physical characteristics of the fabric composing the garment. Several other factors contribute. First, a number of details of the ensemble itself play a role: the composition of the total ensemble worn, design and fit of the single clothing elements, fabric construction, finish applied to the yarn or the fabric, texture of yarn or fibers, yarn construction and fiber type. In addition, a number of factors outside the garment are of importance. It is climatic factors such as h u m i d i t y (moisture/rain), air temperature, radiant temperature and air velocity, and the wearer's activity level (heat production), nature of movements, and compression of the garment. The actual wear situation determines which factors influence the thermal function of the clothing most, and thus thermal comfort. As mentioned above, the inner clothing layer is of importance for our experience of the total clothing worn. Discomfort increases with the level of skin wetness, and an inner clothing layer that can keep the skin dry without itself being sensed as wet will be judged comfortable. An open construction such as fishnet will allow for a more effective ventilation and evaporation from the skin, whereas more sweat will accumulate in and under a tightly knitted construction. The importance of textile material is highly discussed, although wool for centuries has been used for winter clothing, because of its ability to absorb water into its fibers. Newly developed polyester fibers treated with a special finish also seem to keep the skin comfortably dry for longer time than cotton. However, when sweating occurs in a humid en-
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R. Nielsen / Work clothing
vironment the skin will always become soaked and feel uncomfortable.
2.2.2. Freedom of movement During work the body moves, and work clothing should therefore be designed to be worn by a moving body, not restricting movements and not adding any uncomfortable pressure to parts of the body. With tight-fitting work garments there are higher demands on stretchable materials to allow necessary work movements. Figure 3 shows how much the skin stretches in selected positions. In garments the textiles used can seldom stretch so much; only knitted materials allow considerable stretch and they are only suitable for underwear and some types of middle layer. However, a good design can give important extra room at critical places when non-stretchable materials are used. Depending on the design, the fit, the textiles and the interaction of the layers, the final movement will be a combination of stretching, sliding, compression and added pressure on the skin. When the work involves large body movements the design and fit should be such that all single garments are spacious both in length and width, especially at the back, the crotch, the shoulders and the armpits. With work over shoulder level the ensemble should allow good freedom for movements around the shoulder region, and be closable at neck and wrist. Compression of clothing will lower its thermal insulation, allow less air exchange in the clothing compartments, and if the pressure on the skin becomes too high the blood circulation to parts of the skin may be constricted. Dressing/ undressing may in certain areas of a garment
hips : 27 (20) knees : 41 (21)
Fig. 4. Ergonomic details in work clothing.
require more stretching than required when the clothing is worn during work. Wet clothing will often cling together, and the additional friction between the clothing layers may be a constraint during moving. Even in dry clothing each additional clothing layer will increase energy consumption with around 4% due to the increased friction between layers and change of pattern of movements (hobbling gait).
elbows : 50 (24) knees
: 49 (29)
Fig. 3. Stretching of skin in different body positions. The first number is the stretch lengthwise, the second number the stretching across. Attention should be paid to high values at elbows, back, seat and knees in normal work postures.
2.2.3. Ergonomic details in design (figure 4) The most important ergonomic detail is that the sizing is correct. The sizing available on the market is based on standardized anthropometric data. In order to obtain comfort during work it must be possible for the worker to choose the right size, the right length of sleeves and of legs, and the right waist circumference. The height of the worker is not sufficient information for the selection of a well-fitting garment. Different design should be available for the two sexes that takes into account the anatomical differences.
R. Nielsen / Work clothing
To allow freedom of movement in garments produced from non-stretchy material without the garments becoming too bulky, extra cloth partly hidden in pleats is an excellent solution in soft materials at certain sites (a), for example at the back, and between the sleeves and the trunk. Generally, two-piece garments are better in use than overalls since they give more freedom of movements. When an overall is worn, stress often occurs at the back and seat during a forward movement. This can be minimized by introducing a slot between the trouser part and the trunk part, by making a part of the back in an easily stretching textile material (b), or by introducing additional fabric at the back. At knees and elbows, where bent limbs are more common than straight, the design of the garment should include built-in knees and elbows (e). The same principle should be applied in the design of gloves. To prevent unwanted cooling of the lower back, trousers with an elongated waist and braces may be applied (d). Another solution is a sweater with an elongated lower back (e). An outer garment should be easy to open at the neck and in front. To increase the air exchange during high activity, openings in jacket, overall, etc., could be introduced from elbows to waist closed by zippers (f). Combined with an opening at the neck or in front this creates possibility for good ventilation when necessary. When several clothing layers are worn, the outer layer should be designed to give room for inner layers, without being oversize if it is often worn separately. Since bulky outer layers are subject to more stress in extreme situations than central layers, the sizing problem is even more stressed. A hood or a collar should not decrease visibility in any direction. Often the use of a hat and a scarf is better than a hood. Zippers should be sturdy and two-way (g) so they can open from both the top and the bottom, and they should have grips that are easy to handle (h). When gloves are worn during work this is even more important. Velcro closures can often be used instead of buttons, and they are easier to handle (i). However, over time the velcro will catch pile and dirt, and thus become less effective. When used, buttons should not be too small. Pockets should be easily accessible, placed in such a way that they can be reached easily without
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causing the worker to get caught in machines etc. Best are pockets placed on the outside of the thigh/leg (j) or loose slot-pockets (k) placed on the inside because they are easier to get into than other types. When larger items are often placed in the pockets, larger pockets placed outside (I) are preferable because items there will restrict movement less. Also, outside pockets will put less strain on the seams. A good solution is to have a special 'pocket-vest' for tools (m). This vest must be so large that it can be used on top of the most usual garments. In jobs where parts of the work are performed in a kneeling position there ought to be a waterproof reinforcement in the trousers over the knees as a 'knee-pocket' in which a knee-pad could be placed. The opening should be downward so that dirt does not gather in the pocket. In certain types of jobs, such as for example working on a heavily trafficked road or working in the forest, it is important that the worker is easily visible. In these cases orange, yellow or red colors supplemented with stripes of reflecting materials (n) should be used in the outer layer.
2.2.4. Sensoric comfort Sensoric comfort exists when the clothing layer(s) making skin contact do not result in any unpleasant experiences. The fabric should not be scratchy or irritating. In a cool environment a staple yarn like wool results in fewer points of contact between clothing and skin, and is therefore experienced as softer and warmer. However, some people are allergic to wool. When sweating occurs double-faced textiles with a non-absorbent layer facing the skin and an absorbent layer outward seem to decrease an uncomfortable sensation. Often, sweating results in other polluting factors being sensed much more. Also, certain fabrics are sensed as scratchy when the skinclothing interface becomes wet. In the heat a loose-fitting inner layer would allow a pleasant exercise-induced ventilation directly cooling the skin. A fabric that easily clings to the body, and fabrics that cause static electricity when they slide against each other should be avoided. The extra weight of a heavy garment on the shoulders may cause sensoric discomfort locally if the inner layers have a rough texture or otherwise feel unpleasant when pressed towards the skin.
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R. Nielsen / Work clothing
2.3. Protection properties When there is a need for protection against factors in the working environment, this should always be given high priority. The specific protecting ability and fit of work clothing should always be evaluated with regard to the duration of the work and the process or the factor the garment protects against.
2.3.1. Thermal protection In a cold environment two different principles in insulating clothing can be used depending on activity level. When the work is not too physically demanding a heavy quilted thermodress with 'built-in' knees, elbows, etc., is very suitable. This consists of a man-made insulation material sewn in between two layers of textiles, often nylon. This type of clothing is good for work with a constant not too high activity level, for example driving open vehicles, working in high masts, etc. At higher activity levels sweat will occur on the skin and the design of a thermosuit and the low water vapor permeability of the quilt material will often restrict ventilation within the clothing and, thus evaporation from the skin. This may result in accumulation of sweat within the clothing. Another concept is to have one or more insulating middle layer manufactured from pile, wool or a light quilted material. Both wool and pile can capture a lot of air, but for the insulation of the middle layer to be effective a windproof outer layer must prevent the air from penetrating into the middle layers. The outer clothing layer should be designed so as not to compress the underlying layers. Compression will decrease the insulation, something that most people have experienced when sitting on a cold log (a seat constructed from a not easily compressed material such as foam will increase insulation). One problem with this multi-layer system is the bulk of material in armpit and crotch, and the stack of collars and junctions at wrist and ankle. Putting an insulation layer on the inside of a jacket is not a good idea, because the circumference of the insulation is not increased, and thus the insulation is not really increased, but the air is only kept enclosed within the layers. During high level activity in the cold, ventilation of the clothing is needed in order to allow sweat and warm air to escape to the environment and thus
prevent accumulation of sweat in the clothing. In the multi-layer clothing system this can be obtained by opening up the outer layer. A jacket-type with a zipper is therefore more suitable than an anorak-type. At low temperatures the protection of the feet and the hands is often the main problem. Attention should be paid to well insulated boots and good socks (e.g.. polypropylene with wool over). When there is no need for fine operation with the fingers, mittens should be preferred to gloves. Certain jobs may require electrically heated socks and gloves. When work is performed at temperatures well below freezing point for a whole work day, breaks at room temperature are a necessity. During the break the outermost clothing layer worn should be opened and at best taken off so that condensed humidity can easily evaporate. This requires that the garment is easy to open, for example with long zippers that are easy to handle (see example s in figure 4). In cases where the activity level alternates between high and low, the outer clothing layer must be easy to open at wrist, neck, in front, and sometimes also in the armpit for additional ventilation to take place only during high activity. Even so it may be almost impossible to prevent sweat from accumulating in the clothing. It is therefore important to wear an inner layer that has a large buffer capacity and always feels dry. A substantial amount of heat may be lost from the head in cold environments, and it is important to wear a good h a t / s c a r f or hood. A scarf around the neck can prevent air from intruding into the clothing. In situations with high air velocity, when the worker is driving in open vehicles, or when walking a lot. one should be able to close the openings effectively. The uphold of the insulation and thus thickness is important in certain situations, e.g., working in cold water, or when working on one's knees or in a lying position on a cold floor for a longer period. Materials have been specially developed for this use, manufactured with a rigid structure such as the neoprene used in diving suits and the foam used for knee pads. In a warm environment as little clothing as possible should be worn. The clothing worn should be absorbent, for example cotton, and be constructed in an open weave, allowing air to move directly over the skin. The design should be loosefitting. This principle obtains also when more
R. Nielsen / Work clothing
clothing must be worn in a hot environment as protection to other factors. In #ass-works and steel-factories, where large furnaces radiate heat, partly aluminum-covered suits reflecting heat can be recommended; a whole aluminum-covered suit should never be used, because evaporation will then be dramatically decreased. A cotton suit can be covered with the reflecting materials at certain places instead. For short-time operation in a very hot environment clothing insulating against heat in the environment can be necessary, as for example a mantle. Because heat will build up in the body this cannot be worn for long, and it should be very open to allow for convective cooling. For long term work in hot environments conditioned clothing with built-in air or water circulating cooling systems or with ice bags must be applied. For workers with outdoor work, for example on fishing ships, oil riggs, in the forest, etc., protection against rain and wind is important. When working in pouring rain a completely waterproof outer clothing layer is necessary to keep water out. But in a completely waterproof suit condensation of sweat will take place on the inside, and then the wearer becomes wet and cold anyway. Unfortunately, materials that are both waterproof and airy do not exist, although in theory they do. Goretex is one of the breathing materials that has been developed, but although this material allows water vapor to escape through micropores, it is not a perfect solution for a sweating person. The clothing underneath still becomes wet from sweat. As mentioned above large slots for example in the armpits can give considerable ventilation that may prevent or diminish condensation within the clothing. But the three small holes often found at this place in rain wear are of no importance. When working outside on a day when rain only occurs occasionally it should also be remembered that Goretex material restricts evaporation considerably more than a tightly woven cotton/polyester jacket. Another solution is to use a c o t t o n / polyester fabric with a chemical impregnation. Often this can keep rain out for several hours, and the material is far more permeable. When working in a partly wet environment or with wet objects local waterproof protection may be suitable on knees, inside or over the hand, and in front as an apron. As mentioned above, wind (air movements) will
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disturb the insulating air layers, and thus reduce the insulation of clothing. A tightly woven stiff. outer layer together with good closures and a scarf will prevent the air from intruding deeper into the clothing. This layer should preferably be made from cotton, polyester or another material that does not restrict water vapor permeability. Wind results in increased cooling, and in a cold environment head protection and gloves are recommendable to prevent excessive cooling. Working close to a door often means a drafty environment, which requires additional insulation to prevent thermal discomfort.
2.3.2. Protection against hazardous substances
Many workers are exposed to chemicals and other hazardous substances during work. The different substances often require a specific textile or a covered material in the protective garment to prevent diffusion. It should always be indicated against what chemical agent and for how long the clothing protects. The resistant material is often impermeable, and that gives a problem with evaporation through the clothing, as it does not allow any passage of air or water vapor. The missing possibility for evaporation of sweat creates problems for thermoregulation, and requires either use of a work/rest schedule, or the use of a cooling system to prevent excessive heat accumulation in the body when working for longer periods. Efforts have been put into the development of materials that keep the hazardous substances out, but allow water vapor to pass. In a dirty environment the micropores may get closed. Some firms use throw-away suits for certain jobs.
2.3.3. Protection to non-hazardous substances
When considering work clothing for use in a dirty or oily environment, the textile material is of specific importance. It should be tightly woven, and manufactured from a material that allows frequent laundry or dry cleaning without changing the suit's qualities. In some jobs there is danger of ignition of the clothing, and the outer layer must have a low flammability and not be too bulky. If a special protective layer is not worn, pile can be recommended for quilt or wool as it has a lower flammability.
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R. Ntelsen/ Work clothing
2. 4. Laundering properties Laundering is an important and costly aspect in the handling of work clothing. During laundering the clothing ensemble should obviously be cleaned, but it should also retain its original qualities with a minimum of wear and tear. Of special importance is that the garment does not shrink or otherwise change its shape. The clothing must be clean to be accepted by the wearer. The aspects of hygiene are of special importance in areas of food and medical industry, in hospitals, at pharmacies, and so on. However, when workers are exposed to asbestos, lead, and similar hazardous substances cleaning of the clothing used is just as important, because these substances may gather in the fabric. When such substances are present in the work environment laundering should never be left to the worker to do at home, because the hazardous substances may be transferred to the clothing of the rest of the family. The cost of laundering, finishing, storage, and transport amount to at least 55% of the total life span cost for a work clothing ensemble. The life span of an ensemble is essential for its cost, and the life span is dependent on the use of the garment, on the laundering methods, type of machine and intervals between laundering. These are all aspects to be considered when evaluating the investment in new work clothing. 2.5. Wear & tear properties Certain jobs result in a great local wear of the clothing used, while other jobs result in an abnormal general wear. This requires that the clothing is reinforced either locally or generally. The local wear is often at the knees, the elbows or at the shoulders, and at these locations a solution may be a double layer of clothing. When there is a high overall wear of the clothing, the use of a tight-woven polyester mixture may be preferable. In case tools are often used and stored temporarily in pockets, the seams and the fabric around the pockets should be reinforced to allow the extra weight. When the outer garment layer protects against hazardous substances it is important to check regularly that the garment gives sufficient protection.
3. Peripheral body areas (hands & feet) Gloves have a lot of different purposes. They may protect against such different factors as cut, injections, chemicals, vibrations, fire or extremely high temperatures, low temperatures and water. Approximately one third of the accidents at work hurts fingers or hands. If good work gloves are used, it has been evaluated that about one third of the accidents could be avoided. However, badly fitted work gloves have also caused accidents. Good gloves are made for the job they are to be used in; they are manufactured from the right material and have a good fit. Butchers and other workers handling cold wet articles can use thin knitted cotton gloves with thin PVC-gloves over, to protect their hands. This combination can easily be worn under a harness-glove or under a rubber glove used against chemical solutions; the cotton gloves can then be changed several times during the day when wet and the hands can thus be kept dry. For work with less wet articles, for example in forestry, gloves with rubber spots give a better grip, less moistening of the textile material, and less heat loss. For outdoor workers heavier curved gloves with a hard-wearing, water-proof material on the palm are often necessary. Mittens with a slot on the palm side and at the bottom of the thumbs allow the fingers to be free for delicate grips without exposing the whole hand to the cold all the time. The total foot comfort is determined by the interaction between socks, soles and shoes. The shoe itself should be made from a good material, such as leather, and fit well on the foot. It should be large enough for socks and maybe a net sole; it should exist in three different widths and allow the toes to move. At best there should be a velcro or a lace closure so that the shoe can be tightened on the foot. The feet swell considerably during a working day, and a closure enables one to regulate the pressure on the foot. The sole should be stiff under the forefoot, but also allow an easy bend. There should be support for the arc under the foot, and a small heel with rounded back would be good. The sole should be made of a good material and have a profile that prevents sliding on a slippery floor. In the upper part of the shoe small holes in the wails will allow ventilation. In some jobs special protection may be necessary, such as a
R. Nielsen / Work clothing
steel toe, waterproof materials, boots, etc. For indoor office work open net shoes are very comfortable.
4. Data analysis/interpretation Before making a decision on what type of work clothing to buy/use, it is recommended to make an analysis of the worker's job and of his/her work environment. In a work situation the following factors generally determine at least some of the requirements to the use and the suitability of work clothing; and they could roughly be evaluated as;
1. What is the level of physical activity in the job? low/average/high/alternating 2. How is the climatic environment? very cold/cold/indoor ~ outdoor/normal ind o o r / w a r m / v e r y warm 3. How is the level (and type) of pollution the worker is exposed to? low/average/high
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In addition, specific influence and requirements should be noted, as for example body movement/ working body position, what tools and working materials need to be carried during work (need of pockets), need of reinforcements, need of local insulation or protection, etc. After this analysis, specific requirements for the work clothing can be set forward and priorities given. Finally, the clothing available on the market should be analyzed, and a decision can then be made that fulfills the requirements as far as possible. It is important to realize that clothing that seems to have a good fit on a manikin or a professional model does not always fit the normal workers. In certain cases it may be advantageous to contact a manufacturer directly and specify the requirements. The clothing should be purchased in a sufficient number of sizes and different lengths so that it fits everybody in the actual work force.
77
Elsevier Guidelines
Work clothing R u t h Nielsen Laboratory of Heating & Air Conditioning, Technical University o/Denmark, 2800 Lyngby, Denmark
(Received February 5, 1990; accepted February 7, 1990)
1. Identification More than half of the working population uses work clothing of some sort. Work clothing has a shorter lifespan than other ergonomic investments in the work environment and there are therefore good possibilities to change to the best qualities available when new purchases are done. Economic studies have shown that the price of the work garment itself is not the major cost for a company in supplying work clothing to its employees. The basic function of work clothing is to keep the body comfortable with a pleasant thermal micro-climate close to the body, and at the same time to protect the body against injuries, external factors and contact with dirt, dust, chemicals, oil, rain, etc. Depending on whether the requirements to protection, appearance or comfort are dominating the clothing worn is called protective clothing or work clothing. The borders between these two groups are not strict. Ear and eye protection, protective helmets and respiratory masks, security shoes and safety belt with line are examples of protection. Also, clothing to protect against extreme heat and cold or dangerous substances is protective equipment. Work clothing is clothing that should be worn all day, which means clothes that are used in normal (and not extreme) situations. Traditionally, work clothing has also been used to give group identity and to show group membership. Some workers wear uniform, service dress, etc., others use work clothing of a more normal type, and then we find several small groups using very specialized work clothing. However, work clothing does not or should not only include the outer clothing layer we see. It comprises all the 0169-1936/91/$03.50 © 1991 - ElsevierScience Publishers B.V.
different layers in a clothing ensemble worn, and also footwear, hand wear, and head wear.
2. Requirements/function 2.1. General
The requirements to work garments are determined by the interaction between man, clothing and environment. To have an overall good function, the clothing ensemble must have several different qualities (figure 1). Because of the thermal properties of clothing and the interaction with human heat exchange, non-compatible requirements to both material and composition of the clothing often result. Today, many of the protective requirements to the environment can be met; however, the problem is to do it while keeping thermal comfort. Therefore, a work clothing ensemble is often the result of a number of priorities and compromises between requirements to thermal comfort, mobility and different types of protection.
i ON°R,
PROPERTIES
[ TEAR& WEAR] PROPERT'ES I
( ~L~T.,.n ~-.---I COMFORT I PROTECTION PROPERETSI ~
' PROPERTIES I \1 APPEARANCE
Fig. l. Properties ofimponanceforthefuncfionofclothing.
78
R. Nielsen / Work clothing
To dress correctly in a not too hot environment at a low activity is no problem. It is just to dress until not freezing. Problems develop when man in periods performs hard physical work and must get rid of extra heat and sweat, and at the same time must have protection to environmental factors. Here, a few facts on human thermoregulation and heat transport in clothing may be necessary. During physical work, almost all the energy will eventually be converted into heat. During hard industrial work the average heat production of man is often increased 4 - 5 times over the resting value of 60 W / m 2. Some of this heat is used to regulate the body temperature at 37-38°C, the rest should be dissipated to the environment. Whenever the temperature in the environment is lower than skin temperature heat can be given off as a dry heat flow by radiation, convection and conduction through the clothing or directly to the environment from uncovered body areas. When this route of heat dissipation is not sufficient to keep up with heat production, body temperature begins to increase, and sweating will start. Evaporation of
the produced sweat from the skin will take place whenever the relative humidity in the vicinity of the skin is less than 100%. Evaporation of 100 g sweat dissipates 245 k J, so evaporation of sweat is an effective avenue for heat dissipation. If evaporation is restricted (for example by impermeable clothing), the body temperature will increase over its regulated level, and eventually reach levels where heat exhaustion and heat stroke may occur. In warm environments heat may be transmitted from the environment to the skin by radiation, convection or conduction. Thermally, clothing is mainly characterized by resistances to dry and wet heat loss. Each fabric layer is characterized by the two resistances. The resistance to dry heat loss ( - i n s u l a t i o n ) is proportional to the thickness of the fabric layer, whereas for water vapor permeability the construction of the fabric layer is also important. Both for the insulation and the water vapor permeability the thickness of the enclosed air layers in an ensemble is of major importance. Insulation is increased more by a non-moving air layer than
GARMENT
FUNCTION
Underwear Socks (Hat) (Gloves)
Protects and/or ventilates the micro-climate near the skin. Regulates the dissipation of heat and humidity. Important for sensation
Shirt Blouse Sweater atc
Increases heat insulation by creating a non-moving air layer. May absorb end distribute the humidity, ~ may also limit heal dissipation.
Jacket Trousers Vest Skirt Overall
Protects against the environment
,tiv__ee Suit Rain suit Winter coat
Gives an Increased protection against external factor as rain, cold, wind, and hazardous agents.
(Hat) (Gloves)
Fig. 2. A layeredclothing system and the function of each layer.
R. Nielsen / Work clothing
by a textile layer. The vapor permeability is generally more dependent on the fabrics, but it will decrease with increasing thickness of air layers. When man exercises, the air enclosed within the clothing moves, the thermal gradients are disturbed, and air will by forced convective movements be exchanged through openings and directly through fabric layers with air in the environment. This air exchange may amount to more than 100 1/min and it reduces the insulation and increases the vapor permeability of the clothing ensemble considerably. The final exchange is dependent on activity level and pattern, and on the size of the openings. Wind and movements will decrease the insulating air layer sticking to the outside of the clothing, and with an open structure in the outer layer or with large openings wind will penetrate into the clothing, thus increasing heat loss. High air velocities may compress the clothing and thus reduce its insulation because the enclosed air layers are reduced. If clothing gets soaking wet from sweat or water, its insulation decreases. The heat dissipation by evaporation from wet clothing can be considerable, especially when the air velocity is high. However, as this evaporation does not cool the skin directly - only by an increased dry heat loss - it is not so effective. A clothing ensemble should be considered as a multi-layered clothing system comprising an inner layer (underwear), middle layers (e.g., shirt, sweater), and an outer shell layer (e,g., wind breaker, rain gear) (figure 2). Some of the layers may be superfluous in a warm environment, but when all are present in cooler environments each layer serves a specific main purpose. In addition to its hygiene function, the underwear is important for the direct cooling of the skin, for absorbing sweat, and thus, for our sensation of the micro-environment at the skin. The middle layer mainly serves insulating purposes, and the outer layer serve as a protection to environmental factors or as a practical layer for storage of tools etc. A clothing ensemble that should function with high requirements to protection and comfort must be put together methodically from the inside out.
2.2. Comfort properties Comfort in a physical sense means that the body is in a heat balance with the environment
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(thermal comfort), that the body is not subject to pressure from narrow or badly designed clothing (movement comfort), and that skin irritation does not occur from unpleasant contact with the clothing (sensorial comfort).
2.2.1. Thermal comfort Thermal comfort is defined as that condition of mind which expresses satisfaction with the thermal environment. In dressed man this will mostly be determined by the thermal micro-climate at the skin, which results from the thermal function of the clothing worn. The thermal c o m f o r t / d i s c o m f o r t experienced with a clothing ensemble is not only dependent on the physical characteristics of the fabric composing the garment. Several other factors contribute. First, a number of details of the ensemble itself play a role: the composition of the total ensemble worn, design and fit of the single clothing elements, fabric construction, finish applied to the yarn or the fabric, texture of yarn or fibers, yarn construction and fiber type. In addition, a number of factors outside the garment are of importance. It is climatic factors such as h u m i d i t y (moisture/rain), air temperature, radiant temperature and air velocity, and the wearer's activity level (heat production), nature of movements, and compression of the garment. The actual wear situation determines which factors influence the thermal function of the clothing most, and thus thermal comfort. As mentioned above, the inner clothing layer is of importance for our experience of the total clothing worn. Discomfort increases with the level of skin wetness, and an inner clothing layer that can keep the skin dry without itself being sensed as wet will be judged comfortable. An open construction such as fishnet will allow for a more effective ventilation and evaporation from the skin, whereas more sweat will accumulate in and under a tightly knitted construction. The importance of textile material is highly discussed, although wool for centuries has been used for winter clothing, because of its ability to absorb water into its fibers. Newly developed polyester fibers treated with a special finish also seem to keep the skin comfortably dry for longer time than cotton. However, when sweating occurs in a humid en-
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vironment the skin will always become soaked and feel uncomfortable.
2.2.2. Freedom of movement During work the body moves, and work clothing should therefore be designed to be worn by a moving body, not restricting movements and not adding any uncomfortable pressure to parts of the body. With tight-fitting work garments there are higher demands on stretchable materials to allow necessary work movements. Figure 3 shows how much the skin stretches in selected positions. In garments the textiles used can seldom stretch so much; only knitted materials allow considerable stretch and they are only suitable for underwear and some types of middle layer. However, a good design can give important extra room at critical places when non-stretchable materials are used. Depending on the design, the fit, the textiles and the interaction of the layers, the final movement will be a combination of stretching, sliding, compression and added pressure on the skin. When the work involves large body movements the design and fit should be such that all single garments are spacious both in length and width, especially at the back, the crotch, the shoulders and the armpits. With work over shoulder level the ensemble should allow good freedom for movements around the shoulder region, and be closable at neck and wrist. Compression of clothing will lower its thermal insulation, allow less air exchange in the clothing compartments, and if the pressure on the skin becomes too high the blood circulation to parts of the skin may be constricted. Dressing/ undressing may in certain areas of a garment
hips : 27 (20) knees : 41 (21)
Fig. 4. Ergonomic details in work clothing.
require more stretching than required when the clothing is worn during work. Wet clothing will often cling together, and the additional friction between the clothing layers may be a constraint during moving. Even in dry clothing each additional clothing layer will increase energy consumption with around 4% due to the increased friction between layers and change of pattern of movements (hobbling gait).
elbows : 50 (24) knees
: 49 (29)
Fig. 3. Stretching of skin in different body positions. The first number is the stretch lengthwise, the second number the stretching across. Attention should be paid to high values at elbows, back, seat and knees in normal work postures.
2.2.3. Ergonomic details in design (figure 4) The most important ergonomic detail is that the sizing is correct. The sizing available on the market is based on standardized anthropometric data. In order to obtain comfort during work it must be possible for the worker to choose the right size, the right length of sleeves and of legs, and the right waist circumference. The height of the worker is not sufficient information for the selection of a well-fitting garment. Different design should be available for the two sexes that takes into account the anatomical differences.
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To allow freedom of movement in garments produced from non-stretchy material without the garments becoming too bulky, extra cloth partly hidden in pleats is an excellent solution in soft materials at certain sites (a), for example at the back, and between the sleeves and the trunk. Generally, two-piece garments are better in use than overalls since they give more freedom of movements. When an overall is worn, stress often occurs at the back and seat during a forward movement. This can be minimized by introducing a slot between the trouser part and the trunk part, by making a part of the back in an easily stretching textile material (b), or by introducing additional fabric at the back. At knees and elbows, where bent limbs are more common than straight, the design of the garment should include built-in knees and elbows (e). The same principle should be applied in the design of gloves. To prevent unwanted cooling of the lower back, trousers with an elongated waist and braces may be applied (d). Another solution is a sweater with an elongated lower back (e). An outer garment should be easy to open at the neck and in front. To increase the air exchange during high activity, openings in jacket, overall, etc., could be introduced from elbows to waist closed by zippers (f). Combined with an opening at the neck or in front this creates possibility for good ventilation when necessary. When several clothing layers are worn, the outer layer should be designed to give room for inner layers, without being oversize if it is often worn separately. Since bulky outer layers are subject to more stress in extreme situations than central layers, the sizing problem is even more stressed. A hood or a collar should not decrease visibility in any direction. Often the use of a hat and a scarf is better than a hood. Zippers should be sturdy and two-way (g) so they can open from both the top and the bottom, and they should have grips that are easy to handle (h). When gloves are worn during work this is even more important. Velcro closures can often be used instead of buttons, and they are easier to handle (i). However, over time the velcro will catch pile and dirt, and thus become less effective. When used, buttons should not be too small. Pockets should be easily accessible, placed in such a way that they can be reached easily without
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causing the worker to get caught in machines etc. Best are pockets placed on the outside of the thigh/leg (j) or loose slot-pockets (k) placed on the inside because they are easier to get into than other types. When larger items are often placed in the pockets, larger pockets placed outside (I) are preferable because items there will restrict movement less. Also, outside pockets will put less strain on the seams. A good solution is to have a special 'pocket-vest' for tools (m). This vest must be so large that it can be used on top of the most usual garments. In jobs where parts of the work are performed in a kneeling position there ought to be a waterproof reinforcement in the trousers over the knees as a 'knee-pocket' in which a knee-pad could be placed. The opening should be downward so that dirt does not gather in the pocket. In certain types of jobs, such as for example working on a heavily trafficked road or working in the forest, it is important that the worker is easily visible. In these cases orange, yellow or red colors supplemented with stripes of reflecting materials (n) should be used in the outer layer.
2.2.4. Sensoric comfort Sensoric comfort exists when the clothing layer(s) making skin contact do not result in any unpleasant experiences. The fabric should not be scratchy or irritating. In a cool environment a staple yarn like wool results in fewer points of contact between clothing and skin, and is therefore experienced as softer and warmer. However, some people are allergic to wool. When sweating occurs double-faced textiles with a non-absorbent layer facing the skin and an absorbent layer outward seem to decrease an uncomfortable sensation. Often, sweating results in other polluting factors being sensed much more. Also, certain fabrics are sensed as scratchy when the skinclothing interface becomes wet. In the heat a loose-fitting inner layer would allow a pleasant exercise-induced ventilation directly cooling the skin. A fabric that easily clings to the body, and fabrics that cause static electricity when they slide against each other should be avoided. The extra weight of a heavy garment on the shoulders may cause sensoric discomfort locally if the inner layers have a rough texture or otherwise feel unpleasant when pressed towards the skin.
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2.3. Protection properties When there is a need for protection against factors in the working environment, this should always be given high priority. The specific protecting ability and fit of work clothing should always be evaluated with regard to the duration of the work and the process or the factor the garment protects against.
2.3.1. Thermal protection In a cold environment two different principles in insulating clothing can be used depending on activity level. When the work is not too physically demanding a heavy quilted thermodress with 'built-in' knees, elbows, etc., is very suitable. This consists of a man-made insulation material sewn in between two layers of textiles, often nylon. This type of clothing is good for work with a constant not too high activity level, for example driving open vehicles, working in high masts, etc. At higher activity levels sweat will occur on the skin and the design of a thermosuit and the low water vapor permeability of the quilt material will often restrict ventilation within the clothing and, thus evaporation from the skin. This may result in accumulation of sweat within the clothing. Another concept is to have one or more insulating middle layer manufactured from pile, wool or a light quilted material. Both wool and pile can capture a lot of air, but for the insulation of the middle layer to be effective a windproof outer layer must prevent the air from penetrating into the middle layers. The outer clothing layer should be designed so as not to compress the underlying layers. Compression will decrease the insulation, something that most people have experienced when sitting on a cold log (a seat constructed from a not easily compressed material such as foam will increase insulation). One problem with this multi-layer system is the bulk of material in armpit and crotch, and the stack of collars and junctions at wrist and ankle. Putting an insulation layer on the inside of a jacket is not a good idea, because the circumference of the insulation is not increased, and thus the insulation is not really increased, but the air is only kept enclosed within the layers. During high level activity in the cold, ventilation of the clothing is needed in order to allow sweat and warm air to escape to the environment and thus
prevent accumulation of sweat in the clothing. In the multi-layer clothing system this can be obtained by opening up the outer layer. A jacket-type with a zipper is therefore more suitable than an anorak-type. At low temperatures the protection of the feet and the hands is often the main problem. Attention should be paid to well insulated boots and good socks (e.g.. polypropylene with wool over). When there is no need for fine operation with the fingers, mittens should be preferred to gloves. Certain jobs may require electrically heated socks and gloves. When work is performed at temperatures well below freezing point for a whole work day, breaks at room temperature are a necessity. During the break the outermost clothing layer worn should be opened and at best taken off so that condensed humidity can easily evaporate. This requires that the garment is easy to open, for example with long zippers that are easy to handle (see example s in figure 4). In cases where the activity level alternates between high and low, the outer clothing layer must be easy to open at wrist, neck, in front, and sometimes also in the armpit for additional ventilation to take place only during high activity. Even so it may be almost impossible to prevent sweat from accumulating in the clothing. It is therefore important to wear an inner layer that has a large buffer capacity and always feels dry. A substantial amount of heat may be lost from the head in cold environments, and it is important to wear a good h a t / s c a r f or hood. A scarf around the neck can prevent air from intruding into the clothing. In situations with high air velocity, when the worker is driving in open vehicles, or when walking a lot. one should be able to close the openings effectively. The uphold of the insulation and thus thickness is important in certain situations, e.g., working in cold water, or when working on one's knees or in a lying position on a cold floor for a longer period. Materials have been specially developed for this use, manufactured with a rigid structure such as the neoprene used in diving suits and the foam used for knee pads. In a warm environment as little clothing as possible should be worn. The clothing worn should be absorbent, for example cotton, and be constructed in an open weave, allowing air to move directly over the skin. The design should be loosefitting. This principle obtains also when more
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clothing must be worn in a hot environment as protection to other factors. In #ass-works and steel-factories, where large furnaces radiate heat, partly aluminum-covered suits reflecting heat can be recommended; a whole aluminum-covered suit should never be used, because evaporation will then be dramatically decreased. A cotton suit can be covered with the reflecting materials at certain places instead. For short-time operation in a very hot environment clothing insulating against heat in the environment can be necessary, as for example a mantle. Because heat will build up in the body this cannot be worn for long, and it should be very open to allow for convective cooling. For long term work in hot environments conditioned clothing with built-in air or water circulating cooling systems or with ice bags must be applied. For workers with outdoor work, for example on fishing ships, oil riggs, in the forest, etc., protection against rain and wind is important. When working in pouring rain a completely waterproof outer clothing layer is necessary to keep water out. But in a completely waterproof suit condensation of sweat will take place on the inside, and then the wearer becomes wet and cold anyway. Unfortunately, materials that are both waterproof and airy do not exist, although in theory they do. Goretex is one of the breathing materials that has been developed, but although this material allows water vapor to escape through micropores, it is not a perfect solution for a sweating person. The clothing underneath still becomes wet from sweat. As mentioned above large slots for example in the armpits can give considerable ventilation that may prevent or diminish condensation within the clothing. But the three small holes often found at this place in rain wear are of no importance. When working outside on a day when rain only occurs occasionally it should also be remembered that Goretex material restricts evaporation considerably more than a tightly woven cotton/polyester jacket. Another solution is to use a c o t t o n / polyester fabric with a chemical impregnation. Often this can keep rain out for several hours, and the material is far more permeable. When working in a partly wet environment or with wet objects local waterproof protection may be suitable on knees, inside or over the hand, and in front as an apron. As mentioned above, wind (air movements) will
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disturb the insulating air layers, and thus reduce the insulation of clothing. A tightly woven stiff. outer layer together with good closures and a scarf will prevent the air from intruding deeper into the clothing. This layer should preferably be made from cotton, polyester or another material that does not restrict water vapor permeability. Wind results in increased cooling, and in a cold environment head protection and gloves are recommendable to prevent excessive cooling. Working close to a door often means a drafty environment, which requires additional insulation to prevent thermal discomfort.
2.3.2. Protection against hazardous substances
Many workers are exposed to chemicals and other hazardous substances during work. The different substances often require a specific textile or a covered material in the protective garment to prevent diffusion. It should always be indicated against what chemical agent and for how long the clothing protects. The resistant material is often impermeable, and that gives a problem with evaporation through the clothing, as it does not allow any passage of air or water vapor. The missing possibility for evaporation of sweat creates problems for thermoregulation, and requires either use of a work/rest schedule, or the use of a cooling system to prevent excessive heat accumulation in the body when working for longer periods. Efforts have been put into the development of materials that keep the hazardous substances out, but allow water vapor to pass. In a dirty environment the micropores may get closed. Some firms use throw-away suits for certain jobs.
2.3.3. Protection to non-hazardous substances
When considering work clothing for use in a dirty or oily environment, the textile material is of specific importance. It should be tightly woven, and manufactured from a material that allows frequent laundry or dry cleaning without changing the suit's qualities. In some jobs there is danger of ignition of the clothing, and the outer layer must have a low flammability and not be too bulky. If a special protective layer is not worn, pile can be recommended for quilt or wool as it has a lower flammability.
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2. 4. Laundering properties Laundering is an important and costly aspect in the handling of work clothing. During laundering the clothing ensemble should obviously be cleaned, but it should also retain its original qualities with a minimum of wear and tear. Of special importance is that the garment does not shrink or otherwise change its shape. The clothing must be clean to be accepted by the wearer. The aspects of hygiene are of special importance in areas of food and medical industry, in hospitals, at pharmacies, and so on. However, when workers are exposed to asbestos, lead, and similar hazardous substances cleaning of the clothing used is just as important, because these substances may gather in the fabric. When such substances are present in the work environment laundering should never be left to the worker to do at home, because the hazardous substances may be transferred to the clothing of the rest of the family. The cost of laundering, finishing, storage, and transport amount to at least 55% of the total life span cost for a work clothing ensemble. The life span of an ensemble is essential for its cost, and the life span is dependent on the use of the garment, on the laundering methods, type of machine and intervals between laundering. These are all aspects to be considered when evaluating the investment in new work clothing. 2.5. Wear & tear properties Certain jobs result in a great local wear of the clothing used, while other jobs result in an abnormal general wear. This requires that the clothing is reinforced either locally or generally. The local wear is often at the knees, the elbows or at the shoulders, and at these locations a solution may be a double layer of clothing. When there is a high overall wear of the clothing, the use of a tight-woven polyester mixture may be preferable. In case tools are often used and stored temporarily in pockets, the seams and the fabric around the pockets should be reinforced to allow the extra weight. When the outer garment layer protects against hazardous substances it is important to check regularly that the garment gives sufficient protection.
3. Peripheral body areas (hands & feet) Gloves have a lot of different purposes. They may protect against such different factors as cut, injections, chemicals, vibrations, fire or extremely high temperatures, low temperatures and water. Approximately one third of the accidents at work hurts fingers or hands. If good work gloves are used, it has been evaluated that about one third of the accidents could be avoided. However, badly fitted work gloves have also caused accidents. Good gloves are made for the job they are to be used in; they are manufactured from the right material and have a good fit. Butchers and other workers handling cold wet articles can use thin knitted cotton gloves with thin PVC-gloves over, to protect their hands. This combination can easily be worn under a harness-glove or under a rubber glove used against chemical solutions; the cotton gloves can then be changed several times during the day when wet and the hands can thus be kept dry. For work with less wet articles, for example in forestry, gloves with rubber spots give a better grip, less moistening of the textile material, and less heat loss. For outdoor workers heavier curved gloves with a hard-wearing, water-proof material on the palm are often necessary. Mittens with a slot on the palm side and at the bottom of the thumbs allow the fingers to be free for delicate grips without exposing the whole hand to the cold all the time. The total foot comfort is determined by the interaction between socks, soles and shoes. The shoe itself should be made from a good material, such as leather, and fit well on the foot. It should be large enough for socks and maybe a net sole; it should exist in three different widths and allow the toes to move. At best there should be a velcro or a lace closure so that the shoe can be tightened on the foot. The feet swell considerably during a working day, and a closure enables one to regulate the pressure on the foot. The sole should be stiff under the forefoot, but also allow an easy bend. There should be support for the arc under the foot, and a small heel with rounded back would be good. The sole should be made of a good material and have a profile that prevents sliding on a slippery floor. In the upper part of the shoe small holes in the wails will allow ventilation. In some jobs special protection may be necessary, such as a
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steel toe, waterproof materials, boots, etc. For indoor office work open net shoes are very comfortable.
4. Data analysis/interpretation Before making a decision on what type of work clothing to buy/use, it is recommended to make an analysis of the worker's job and of his/her work environment. In a work situation the following factors generally determine at least some of the requirements to the use and the suitability of work clothing; and they could roughly be evaluated as;
1. What is the level of physical activity in the job? low/average/high/alternating 2. How is the climatic environment? very cold/cold/indoor ~ outdoor/normal ind o o r / w a r m / v e r y warm 3. How is the level (and type) of pollution the worker is exposed to? low/average/high
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In addition, specific influence and requirements should be noted, as for example body movement/ working body position, what tools and working materials need to be carried during work (need of pockets), need of reinforcements, need of local insulation or protection, etc. After this analysis, specific requirements for the work clothing can be set forward and priorities given. Finally, the clothing available on the market should be analyzed, and a decision can then be made that fulfills the requirements as far as possible. It is important to realize that clothing that seems to have a good fit on a manikin or a professional model does not always fit the normal workers. In certain cases it may be advantageous to contact a manufacturer directly and specify the requirements. The clothing should be purchased in a sufficient number of sizes and different lengths so that it fits everybody in the actual work force.