Seating at work: ergonomic selection and adjustment

Health and Safety Executive Figure 3 Dimensions of and relationship between chair and worksurface 36 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. 37 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. Further guidelines for lifting loads are covered by the Manual Handling Regulations 1992 (see Appendix 1). 38 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. 39 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. Further guidance on lighting can be found in HSE’s booklet Lighting at work (see Appendix 3) 400 400 300 300 zone of convenient reach 200 200 normal working area 100 100 700 600 500 400 300 200 100 0 100 200 300 400 500 600 700 all dimensions in millimetres edge of worksurface Figure 4 Reach in the horizontal plane. (The distances shown can be reached by 95% of women) Seating at work Page 12 of 22