Comfortable and adjustable
In general, office chairs fit 90% to 95% of the adult population. People who are taller, shorter or larger than most of the population or have special requirements may require seating specifically made to suit their needs.
Seating should be comfortable, appropriate to the task and easy for the operator to adjust. There is a common belief that seated people tend to maintain a fixed posture for long periods. However, people performing a range of activities tend to adopt different positions and postures while seated. Sitting in different postures is desirable because it varies the load on the thighs and back and can improve seating comfort in general.
Appropriate office chairs
Key factors to consider when deciding whether an office chair is appropriate for the employee and the job include the following:
- it should be adjustable to the task and easily adjusted from the seated position
- the seat should be height-adjustable, preferably using a gas lift for ease of adjustment
- the seat should have a curved front edge to minimise pressure on the underside of the thighs
- the seat should be able to tilt slightly backwards or forwards
- it should have a supportive backrest that is adjustable in height, angle and depth
- both the seat and backrest should be covered by cloth or some other type of material that breathes
- it should have a 5-point wheel base for stability
- armrests are optional
- Armrests help decrease forces on the shoulders and back during rest from keying.
- However, they can interfere or get caught under the edge of the desk and stop the chair from being positioned correctly.
- If provided, armrests should be height-adjustable.
Chairs should support the body in a way that minimises awkward postures and provides comfort. However, no chair can provide a perfect position for long periods. It is important to change positions and get up from a chair many times during the day.
Remember to try to avoid sitting for long periods of time. Some form of break from sitting every 20 to 30 minutes is helpful. Even getting up for 20 to 30 seconds to go to a printer or standing while talking on the telephone will provide relief.
The design of some alternative seating causes people to sit with their hips at an angle they believe will reduce pressure on the lower back. These seats may not provide the best support or allow for a change of position in the chair where employees sit for many hours of the day.
There are no current guidelines or design standards for alternative chairs and they should not be used for constant sitting. Conventional office chairs are required in the office workplace.
Examples of alternative seating include:
- the 'kneeling' chair, a forward-tilted chair base with knee support
- the 'sit-stand' or 'saddle' chair with a tilted base for 'propping' on
- the 'physio' or 'fit' ball, an inflated ball which encourages constant small changes in posture to maintain balance
- executive chairs, which, as the name suggests, are designed as status furniture for executives
It is important to note there is little, if any, evidence of scientific trials or studies suggesting fit balls, also known as 'fitness', 'Swiss', or 'exercise' balls, are suitable for daily use as work seats. For more information, refer to WorkSafe's guidance Fitness Balls are Not Suitable as Chairs.
Alternative seating limitations
An organisation may choose not to allow alternative seating unless the seating has been assessed for risks to users or is required by a medical or rehabilitation plan.
There are limitations in using alternative seating in the workplace. For example:
- often the user cannot adjust the height or the angle of seat, although some models of 'kneeling' and 'sit-stand' chairs do provide adjustments and include an adjustable backrest
- alternative chairs often rely on a set posture, keeping the natural curves in the back. Users may need to gradually increase the use of this type of seating so their muscles become comfortable with the different postures
- although some of these postures may be preferred for short periods, in general these forms of alternative seating do not provide lumbar support. If a chair does not have lumbar support, the employee's back and abdominal muscles must work for long periods to maintain the posture
- getting on and off and sitting on seats such as the 'kneeling' chair and 'fit' balls may be awkward, particularly with some types of clothing. Users should be careful when using such seats
- where there is no stable mobile chair base, a person cannot easily move around the workstation because their leg positions are often constrained. They must rely on back and arm strength to move
- the design of executive chairs often provides little adjustability or seat and backrest design support. Because most senior managers use computer equipment as a core part of their daily work, executive chairs should include the adjustability and features listed
Although alternative chairs allow an upright posture when facing a task, they tend to require users to reach, bend and twist more to access other parts of the workstation. There may be risks from loss of balance and injury through users needing to position themselves in 'extreme' postures.
How to correctly adjust an office chair
- Adjust the chair height so the thighs are approximately horizontal and the feet rest comfortably on the floor.
- Adjust the chair and desk so the work is at elbow height. Where employees perform writing and mouse and keyboard tasks, it may be necessary for the user to adjust chair height slightly between the two tasks - raised for keying or mouse work and lowered for writing.
- If the chair height is correct but the desk is too high, either lower the desk height or raise the height of the chair. Use a footrest to make up the height difference so the user's thighs are horizontal to the floor.
- Adjust the backrest so its curve fits into the curve of the lower back, centred about waist level. A slight backwards tilt of the backrest or forward tilt of the seat will allow an increase in the angle at the hip. This will decrease the force on the lumbar spine.
- If the thighs are wedged between the chair and the under surface of the desk, or the knees bump into the front of the desk, then either the desk is too low, the chair is too high, the desk top is too thick or the user is too tall for the chair and desk. An ergonomist can give advice in this situation.
- Users can make small adjustments whenever they change tasks so they have the most appropriate posture for the task.
How to decide whether you need a footrest
Whether you need a footrest will depend upon whether your desk is at the required height once you have adjusted the chair to suit your needs. If the desk is too high and cannot be lowered, then raise the height of the chair and use a footrest to raise the height of the floor by the same amount. Footrests should be height and angle adjustable and large enough to permit some movement while supporting the feet. A footrest should not be so big that it clashes with the chair base. Using a footrest limits mobility, so it is better to have a fully adjustable desk and chair so a footrest is not necessary.
Image: Seat height and footrest adjustment.
How to decide whether you need armrests
Armrests allow people to support themselves when getting up or sitting down. They are suitable for employees who perform a variety of tasks at a workstation, move frequently to and from their chair or sit back in their chair to talk to visitors. Armrests are less suitable for keyboard work. If the elbows are fixed on the armrests they can cause the shoulders to rise into an unnatural posture. The desk surface can support the forearms and reduce the effort of supporting the arms. Armrest designs should not limit forward chair movement and should not touch the desk.
Choosing between castors and glides
Castors allow users to move chairs forwards and backwards easily. However, they are not suitable for use on non-carpeted surfaces unless the castors have friction brakes. Misuse of a chair with castors, such as by standing on it, is hazardous. Chairs that do not need to move, such as visitors' chairs or on hardwood surfaces, should have glides or castors with friction brakes. It is important not to provide slippery mats at desks where chairs with castors are in use.
Assessments before buying chairs
Before buying new chairs, it is important to assess use of the chairs and the design features needed. The requirements for adjustable-height chairs are in the Australian/New Zealand Standard AS/NZS 4438:1997 (R2016) Height adjustable swivel chairs. It is the responsibility of suppliers to advise if chairs meet the Australasian Furnishing Research and Development Institute (AFRDI) Standards. Trial use of chairs in the office is advisable before purchase.
Your legal duties
The Occupational Health and Safety Act 2004 (OHS Act) requires employers to provide and maintain a working environment that is safe and without risks to health, including psychological health, so far as reasonably practicable. This responsibility includes providing and maintaining safe systems of work and an obligation to consult with employees and health and safety representatives (HSRs) on matters that directly affect or are likely to affect their health or safety.
Employees also have duties under the OHS Act to take reasonable care for their own health and safety, the health and safety of people in the workplace and to co-operate with their employer.
Find out more about office work and your legal obligations on the WorkSafe website page, The Risk Management Approach to Health and Safety. A link to the page appears in Related information.
Australian/New Zealand Standard
- AS/NZS 4438:1997 (R2016) Height adjustable swivel chairs.
- Australasian Furnishing Research and Development Institute (AFRDI) Standards.
The risk management approach to health and safety
Identifying hazards in the office
Developing a health and safety policy
Physical factors in office work
Office work and mental health
Thermal comfort and air quality in offices
Office layout and design
Office workstation design
Desks, workstations and workbenches
Health and safety with keyboards, the mouse and other pointing devices
Telephones and mobile phones
Different types of office work
Using office equipment safely
Storage and moving systems
Working with computers
General office health and safety
Exercises for office employees
Using copiers, printers and similar equipment