Working with computers can cause workers a number of problems. These include stress, visual discomfort, as well as aches and pains in the hands, wrists, arms or shoulders.
The ACTU has Guidelines on Screen Based Work [pdf]. The guidelines, although developed some years ago, provide information on a range of issues associated with screen based work, including the ergonomics of the work station, electro-magnetic radiation and so on.
Computer Workstation Dimensions
(Based on the Australian Standard AS 3590 - 1990 Screen based workstations, part 2 workstation furniture)
Height of work surface
- If fixed - 680mm to 720mm above floor level
- If adjustable - 580mm - 730mm above floor level
Area of work surface
- Width - 1500mm minimum
- Depth - 900mm minimum
- Bench thickness over leg span - 25mm maximum
Volume of leg space
- Width - 800mm minimum
- Depth - 550mm minimum
- Height - 580mm minimum
Viewing distance to work
- 350mm - minimum
- 750mm - maximum
- Height of display - 30mm - 40mm below eye level
- Surface of seat to floor - 380mm - 510mm
- Seat pan depth - 330mm - 430mm
- Footrest area - 300mm x 375mm
Chairs and Posture Checklist for Keyboard Workers
It is important to ensure that the chairs are well adjusted chairs - this improves body position and circulation, reduces muscular effort and decreases pressure on the worker's back. Chairs should swivel, have five wheels for stability, have breathable fabric on the seat, a rounded front edge and have adjustable height and backrest for lumbar support.
Work surface height
The height of the work surface and/or the chair should be such that the work surface is approximately at finger length below the height of the elbow when seated.
The seat tilt should be adjusted so that the worker is comfortable when using the keyboard. Usually this will be close to horizontal but tilted slightly forwards. If this places an uncomfortable strain on the leg muscles or if the feet do not reach the floor then a footrest should be used. The backrest should supports the lower back when the worker is sitting upright.
The keyboard should be in a position that allows the forearms to be close to the horizontal and the wrists to be straight. That is, with the hand in line with the forearm. If this causes the elbows to be held far out from the side of the body then the work surface height should be re-checked.
The eye to screen distance should be set at the distance that permits the worker to most easily focus on the screen. Usually this will be within an arm's length. The height of the monitor should be such that the top of the screen is below eye level and the bottom of the screen can be read without a marked inclination of the head. Usually this means that the centre of the screen will need to be near shoulder height.
All controls and task materials should be placed within a comfortable reach of both hands so that there is no unnecessary twisting of any part of the body.
The document holder should be placed close to the monitor screen in the position that causes the least twisting or inclination of the head.
Posture and environment
Workers should change posture at frequent intervals to minimise fatigue and avoid awkward postures at the extremes of the joint range, especially the wrists. It is best to take frequent short rest breaks rather than infrequent longer ones ( see the ACTU Policy). Sharp increases in work rate are to be avoided - changes should be gradual enough to ensure that the workload does not result in excessive fatigue. After prolonged absences from work the overall duration of periods of keyboard work should be increased gradually if conditions permit.
Lighting for VDUs
VDUs should be placed to the side of the light source/s, not directly underneath. If possible, desks should be sited between rows of lights. If the lighting is fluorescent strip lighting, the sides of the desks should be parallel with the lights. Screens should not be placed near windows but if this is unavoidable neither the screen nor the operator should face the window.
If the VDU is well away from windows, there are no other sources of bright light and prolonged desk-work is the norm, a low level of service light of 300 lux should be used. If there are strongly contrasting light levels, then a moderate level of lighting of 400 - 500 lux may be desirable but high quality anti-glare screens may be necessary.
Glare and reflection
It is important to detect the presence of glare and reflection. To determine whether there is glare from overhead lights the seated worker should hold an object such as a book above the eyes at eyebrow level and establish whether the screen image becomes clearer in the absence of overhead glare. To detect whether there are reflections from the desk surface the worker should hold the book above the surface and assess the change in reflected glare from the screen.
A number of ways are available to eliminate or reduce the influence of these reflections:
- Tilting the screen so that the reflections are directed below eye level.
- Purchasing a screen with matt or light diffusing surfaces.
- A negative contrast screen (dark characters on light background) will reduce the influence of these reflections.
Note: Covering the screen with a light diffusing surface or anti-glare screen is no longer recommended.
If the worker experiences eye discomfort when using a bright screen the following adjustments should be made:
- Turning the screen brightness down to a comfortable level.
- Looking away into the distance in order to rest the eyes for a short while every ten minutes or so.
- Changing the text and background colours. Recommended are black characters on white or yellow background, or yellow on black, white on black, white on blue and green on white. Avoid red and green and yellow on white.
Using a mouse
A well designed mouse should not cause undue pressure on the wrist and forearm muscles. A large bulky mouse may keep the wrist continuously bent at an uncomfortable angle. Pressure can be reduced by releasing the mouse at frequent intervals, by selecting a slim-line, low-profile mouse and by using the mouse at a comfortable distance from the body.
See also the following Australian Standards:
- AS/NZS 4443: 1997 Office panel systems - Workstations
- AS/NZS 4442: 1997 Office desks
Keyboard equipment and radiation
VDUs emit radiation, particularly visible light which allows the characters on the screen to be seen. Weak electromagnetic fields and very low levels of other radiation, not visible to the human eye, can be detected by sensitive instruments. Similar emissions are produced by television receivers.
However, the levels of most radiations and electromagnetic fields emitted from VDUs are much less than those from natural sources, such as the sun - and are well below levels considered to be harmful by responsible expert bodies such as th International Radiation Protection Association (IRPA).
The weak electromagnetic fields produced by television receivers and VDUs extend in all directions, but their intensity decreases very quickly with distance from the source. A workplace should be organised to ensure that VDU operators are no closer to any other VDUs than they are to their own.
Flat screen displays, such as liquid-crystal displays used in some laptop/notebook computers, produce even smaller amounts of radiation than those which use television type tubes.
Note: concerns have been raised that radiation from VDUs is a cause of cancer, however research to date has failed to establish a causal link.
Keyboard and telephone operations
Lightweight adjustable headsets with a volume control should be provided for staff on continuous keyboard/telephone operation. For continuous, traffic dependent telephone operations a manual call facility should also be provided.
- Office wise: A Guide To Health And Safety In Offices. This is a WorkSafe publication picked up in all jurisdictions which provides information on a range of office issues. It is also available (free) from WorkSafe (03 9641 1555).
- From the Trade Union Congress supported Hazards Magazine, resources on Computer Workstations including links to international on-line checklists and research tools.
- From the UK's Health and Safety Executive (HSE)
- Working with VDUs [pdf] - a 16 page booklet
- Display screen equipment workstation checklist - A display screen equipment assessment checklist to help in the assessment of the risks to workers from visual display units and to comply with (UK) legal requirements
- more resources from the HSE can be downloaded from this page.
- From the US Occupational Safety and Health Administration (OSHA) an eTool that illustrates simple, inexpensive principles that will help workers and employers create a safe and comfortable computer workstation.
- From British Columbia (Canada), a useful publication How to Make Your Computer Workstation Fit You [pdf] which provides advice on adjusting the workstation, a checklist and also some exercises.
What about laptop/notebook computers?
Laptops, notebooks and iPads are increasingly being used to work away from 'permanent' workstations. Where possible and practicable it is advisable that all of the principles applying to computer workstations be applied when working with these types of computers. It is particularly important to avoid awkward body postures and ensure that frequent short breaks are taken to minimise the onset of fatigue.
For more information check out the following:
- Laptop, netbooks and iPad Hazard Guide - from the Victorian Government Department of Education and Early Childhood Development (scroll down the page)
- Guidance Notes concerning Safe Use of Laptops and Notebooks [pdf] - from Manchester Metropolitan University
- The Ergonomics of being mobile - a leaflet produced by ergonomic office - a commercial enterprise.
Last amended November 2016