What the law says
The Health and Safety (Display Screen Equipment) Regulations 1992 apply to workers who use a computer, laptop, tablet or smartphone for work every day, for an hour or more at a time. The Health and Safety Executive calls them display screen equipment users. For them an employer must:
- carry out an assessment of the workstation, chair included;
- reduce the risks it finds, which includes seeing that people take breaks from screen work or change task;
- provide an eye test when a user asks for one; and
- give training and information.
The executive states that the law covers home workers and mobile workers as well as those at a fixed desk. Where someone works both at home and in the office, the assessment covers both. A worker's own furniture may be adequate; where the assessment shows that equipment is needed, the executive's guidance is explicit that workers cannot be charged for it. Its guidance is published as working safely with display screen equipment.
The self-employed are outside these duties and have to make the same judgements for themselves.
What a work chair needs
A chair for a working day at a desk has five things that a dining chair lacks:
- A seat that adjusts in height, on a gas lift.
- A back rest that adjusts in height and in tilt, shaped to support the lower back.
- A stable base — five feet, on castors suited to the floor: hard castors for carpet, soft ones for hard floors.
- A seat of the right depth, or one that slides, so that the back rest can be reached without the front edge pressing behind the knees.
- Armrests that adjust or come off. Fixed armrests that stop the chair going under the desk do more harm than good.
Chairs for office use are tested to the European standard EN 1335, which sets dimensions, strength and stability, and the label states the weight the chair is built for. Mesh or upholstery, a headrest, and the various tilting mechanisms are matters of preference.
Setting it up
The executive's advice on posture, in the order in which the adjustments are made:
- Seat height is set so that the thighs are supported evenly from front to back and the shoulders are relaxed, not hunched, with the keyboard just below elbow height.
- Seat depth leaves a gap of two to three centimetres between the front of the seat and the back of the knee.
- The back rest supports the lower back; a cushion makes up the difference where it does not.
- The screen stands directly in front, with its top level with the eyes and about an arm's length away.
- The keyboard and mouse are central and close, the mouse in line with the elbow.
If a seat set at the right height for the desk leaves the feet off the floor, a footrest is the answer, not a lower seat.
A laptop used for long periods needs a separate keyboard and mouse, so that the screen can be raised on a stand to eye level.
Getting out of it
No chair makes sitting still for hours harmless. The regulations require breaks or changes of activity, and the usual guidance is that short breaks taken often are better than long ones taken rarely. Desks that rise to standing height serve the same purpose, by changing posture; standing all day is no improvement on sitting all day.
Buying one
- Try it. Bodies differ, and ten minutes sitting in a chair tells more than its specification.
- Check the range of adjustment against the people who will use it. Very tall and very short users fall outside the range of many standard chairs.
- Second-hand chairs from office clearances are often of far better quality than new ones at the same outlay. The gas lift should hold its height under load, every lever should work, and any upholstered chair should carry its fire safety label.
- Chairs sold for gaming are built to look like racing seats. Their fixed shaping suits some people and not others, and the same tests apply.
Desks, storage and the rest are covered under office furniture.