Seat (see figure 1(a))The seat needs to adjust in height to meet the needs of a range of users. The size of the seat needs to be wide enough to seat big people comfortably and deep enough to support the legs of tall people, but not so deep that shorter workers cannot use the backrest. The surface of the seat should not be hollowed or deeply shaped, as this makes it harder to get up or change position. The front edge of the seat needs to be rounded-over and well-padded to prevent it digging into the thighs.
BackrestThe backrest needs to give firm support to the lower and the middle part of the back. Height adjustment is recommended unless the backrest is high and provides complete support for the back. There should be adequate space for the buttocks; this is usually achieved by leaving a gap between the seat and the backrest. Backrests which tilt with the worker, or whose angle can be adjusted, can improve comfort by providing support for the back in a range of working positions.
ArmrestsFor most jobs armrests are not essential. They can restrict arm movement, although for many jobs they can provide comfort. They should be set back from the front edge of the seat, or be adjustable to allow the chair to be drawn up close to the work surface. The height of armrests should not be too low or too high (see figure 1(b)) to cause discomfort.
FootrestsAny worker who cannot easily place their feet flat on the ground, when using the seat adjusted to the correct working height, needs a footrest. This should be large enough to allow for foot movement. Adjustable footrests of a selection of heights are preferred. Free-standing footrests should not be so light that they move accidentally.
MobilitySwivel-action chairs provide flexibility when the worker needs to conduct a variety of tasks and move from one location to another. Ensure that chairs with castors do not slide away too easily when the user gets up or sits down. This a common problem when they are used on hard floors, or with chairs with a high or tilting seat. Different types of castors are available for different floor types, such as hard floors and carpeted floors. In certain situations glides are safer to use than castors. Ensure that the correct ones are chosen to meet workplace needs. Some seating is designed so that a brake is applied when the chair is sat on, or when the user gets up.
AdjustabilityThe commonest adjustments included in seating design are seat height, backrest height and tilt. In some chairs the seat and backrest can tilt forward together; this feature can reduce neck discomfort and also improve the worker’s reach over the work surface. Some backrests can be adjusted backwards and forwards to change the depth of the seat to meet individual needs. Armrests can be designed to be adjustable to aid work that requires a steady arm position, and to provide for a better match between the needs of the user, their workstation and the task (see figure 2).
Adjustment controls should be easy and convenient to use from a sitting position, especially where the workspace is confined. Controls must be sturdy and reliable. For example, when adjustments are made they must be able to withstand the worker’s weight to prevent a slip or failure which may lead to an injury. Mechanisms need to be designed to prevent workers from trapping their fingers when making adjustments to the seating.
Gas lift chairsSome pedestal chairs have compressed gas in a cylinder under the seat to enable seat height adjustment. Care should be taken with these chairs. There have been incidents where the cylinder has failed through metal fatigue, causing parts to be forcefully expelled. The following guidelines apply to all gas pedestal chairs:
- if the seat wobbles suddenly, or tips, do not examine it or try to fix it. Contact the supplier or manufacturer immediately to ensure that the chair receives expert attention;
- nobody weighing more than 100 kg (16 stone) should use a gas lift chair unless it has been specially designed to accommodate heavier people safely;
- the chair must not be misused, and it should be well-maintained (see paragraphs below on seating maintenance);
- the supplier should be contacted if any defect is noticed and before having the chair renovated.
UpholsteryThe seat, armrests and backrests should be well padded to ensure that the worker’s body does not press uncomfortably on the frame of the chair. Corners and edges of chairs should be well padded to reduce the likelihood of damage. Padding needs to be firm rather than soft, and of good quality to ensure that the chair remains comfortable for a reasonable time. If flexible polyurethane foam is used, it should comply with the requirements in BS 3379, or an equivalent standard.
Chair covers need to be non-slip, easy to clean or wash, and of a fabric which ‘breathes’ (permeable to moisture). Good-quality, durable covers will aid comfort and prolong the service life of the chair. Moulded armrests can be a good alternative to the upholstered sort. Chairs with removable covers are useful in dirty and dusty environments because they can be washed and cleaned regularly. Alternatively, PVC-covered or moulded plastic chairs can be used since they may be easily wiped down or spot cleaned, although they are less comfortable to sit in for long periods particularly in warm or humid atmospheres, or in very warm or cold conditions.
DurabilitySeating at work needs to be strong and stable since it is used for long periods. It is recommended that chairs pass the tests laid down in BS 5459 or an equivalent standard. This helps eliminate any design or manufacturing weakness which may cause failure or possible injury.
Planning the workstationWorkstation design should be based on a careful assessment of all aspects of the job, and any special needs of the individual worker. Ensure that each task can be carried out safely, comfortably and as efficiently as possible.A well-designed workstation allows the worker to be seated at a comfortable height and position in relation to the work (see figure 3). Recommended dimensions for seat height are in this guidance (see figure 1(a)). Work and equipment that is used frequently needs to be placed within easy reach to prevent awkward stretching and twisting which could lead to back pain or injury (see figures 4 and 5). The height of the workstation and seat should ensure that hand work can normally be done at elbow level or below to prevent tiredness from constant raising of the forearm. Some high-precision tasks which require close hand-eye coordination will require a higher hand position: if such work is carried out for any length of time special arrangements to support the arms may also be necessary.
If any lifting is required, the equipment and workstation should be arranged to allow the object to be kept close to the body, and to keep twisting or stretching to a minimum. Lifting even fairly light objects when seated should be kept to a minimum as this can place a strain on the back.
Work surface thickness should be the minimum necessary to provide adequate strength. A typical maximum is 30 mm. Surfaces thicker than this tend to restrict the number of people who can sit comfortably at the workstation because it does not provide sufficient clearance for the thighs while allowing the hands to be at around elbow height. The workstation also needs to be sufficiently sized to allow the work equipment to be used safely. For instance, there should be enough space to place equipment such as visual display units at the appropriate distance, whilst still allowing room for using hands.
Lighting in the workplace also needs to be suitably positioned and sufficient for the task to prevent workers from taking up awkward postures in order to see properly.
Should people sit or stand?People find it more comfortable to sit rather than stand whilst working, unless the type of work requires constant stretching or twisting to reach or lift objects (see figure 6). Employers therefore need to ensure that work is organised to allow people to be seated wherever possible. In circumstances where sitting is not possible, for instance where work has to be done over a large area or where constant handling of heavy objects cannot be avoided, standing may be preferable. In this case, employers need to ensure that workers take adequate rest breaks and that suitable comfortable seating is provided during those breaks.Standing or sitting for long periods can lead to discomfort and may result in long-term health problems, so it is important that workers have the opportunity to change position, stand up and move around. If possible the workstation and seating design should allow for free movement. If this is not possible, an employer can provide opportunities for movement by giving employees a variety of tasks or introducing task rotation, or by ensuring that employees take adequate rest breaks away from the workstation.
Prevention is better than cureEmployers need to be able to spot the signs that suggest seating is uncomfortable. For example, people may use cushions of their own or makeshift footrests. Simply asking employees if their seat is comfortable is sometimes enough to assess whether a problem exists. It is better for employers to take the initiative in providing suitable seating, and not wait until complaints are received or until workers take time off with back pain. Employees also need to play their part by telling their employers, or those responsible for health and safety, if seating is unsuitable or unsafe.
Selection of seatingParagraphs above cover the steps that an employer can take when selecting seating. This can involve carrying out user trials. For example, people of different shapes and sizes could try out a sample seat for a period. Some suppliers may be willing to supply seating on approval. Nevertheless, it is recommended that employees and safety representatives are consulted on any changes to be made to the workplace or workstation, and this includes seating.
Seating maintenanceTo ensure that seating is safe and has a good service life, it must be treated properly. It is bad practice to put undue pressure on the armrests by sitting on them, or leaning too heavily over them. Rocking backwards and forwards may cause damage or cause the seat to become unsafe, as may standing on it to move furniture or equipment.
Employers need to ensure that seating remains in a clean, safe condition. It is good practice to check seating regularly for signs of damage or excessive wear. Particular attention should be paid to the adjustment mechanisms, which should be serviced or repaired as necessary. Unsafe seating should be removed or made safe.
Examples of seating and workstation layout
Machinery workWhere employees are operating or monitoring machinery it may not always be possible to provide a standard chair. Wherever possible employers need to provide some form of suitable and safe seating. Several designs may be suitable (see the following paragraphs). Chairs will need to meet the safety requirements of the task at hand. For example, chairs will need to be adjustable or of the correct height for the task to prevent workers from over-reaching, stretching and twisting. It can sometimes be advantageous for the workstation to be arranged to allow workers to sit or stand alternately. Hand controls should be within easy reach and ergonomically designed. Sufficient room needs to be provided for knees and legs.
If material needs to be fed into a machine, bending can be avoided by having the material at waist height on a rack, which can be raised as the pile of material reduces. Foot pedals need to be arranged at the same level as any footrests to prevent constant bending or lifting and lowering of the legs.
Lean-on or sit-stand seats (see figure 7(a))These seats are suitable only when it is impracticable to use conventional seating, and when machinery and the workstation does not allow for knee space. Such seats should still be adjustable in height and arranged to take part of the body’s weight. Particular attention should be paid to ensuring such seats are stable and comfortable under the conditions of use.
Wheeled, sliding or suspended seats (see figure 7(b))These can be useful when employees need to move frequently from one machine or location to another.
Fixed, foldaway seats (see figure 7(c))These may be more appropriate where space does not allow for common chair dimensions. The design can be swing-out or flap-down and can be tucked away when out of use.
Process work (see figures 8 and 9)If a job involves a series of tasks, the work can be arranged in a semicircle around the worker rather than in a straight line. A swivel chair can be provided so that all points on the semicircle can be reached from a sitting position. It is easier and quicker for the work to be at close hand; turntables, jigs and holders can all be used to ensure this. Chairs with a forward-tilting seat and backrest can provide support if the task requires reaching. Using a slightly sloping work surface or sloping component trays can also provide support as well as added comfort.
Precision workWorkers on precision work which requires a great deal of concentration tend to lean forward and adopt a tense posture (also see figure 9). Chairs with a forward-tilting seat and backrest, and/or a work surface which slopes towards the worker help to avoid this problem and are recommended for this type of work.
Keyboard work/visual display unit (VDU) workParagraphs below can be followed to check that seating for keyboard or VDU work is suitable. The Health and Safety (Display Screen Equipment) Regulations 1992 and associated guidance provide further information. In general:
- seating should be adjustable to allow the hands to work at elbow height. There should be room for the legs to fit comfortably under the desk (see figure 10);
- armrests should not prevent the user from getting close to the workstation when using a keyboard or other input device (eg mouse);
- it should be possible to place the feet flat and comfortably on the floor, otherwise a footrest should be provided;
- the backrest should be adjustable and provide adequate support for the user. The small of the back should be supported by the chair and the shoulders should be relaxed.
Checkout workThis type of workstation can vary in design. Common problems include limited space for movement and the user having to deal with a variety of tasks. Choosing a fairly compact seating design with easily accessible adjustment controls for the seat and backrest can be a solution (see figure 11).
Certain design features are important for checkout work:
- upholstery needs to be comfortable, durable and easy to clean;
- the seat should swivel, adjust in height, be well-padded, and preferably be forward-tilting;
- the backrest should be adjustable in height, depth and tilt;
- an adjustable footrest will be necessary as the chair is likely to be used by a variety of people.
Back safety tips: Simple measures to protect yourselfBack injuries are prevalent among all workers. This video covers simple measures you can take to protect yourself.
Back Safety tips to keep in mind:
- Practice good posture
- Exercise & Streching
- Move around every 30′