A Guide to Work with Computers

A Guide to Work
with Computers
This guide is prepared by the Occupational Safety and Health Branch, Labour Department
This edition
May 2010
This guide is issued free of charge and can be obtained from offices of the Occupational
Safety and Health Branch of the Labour Department. It can also be downloaded from
website of the Labour Department at http://www.labour.gov.hk. For enquiries about
addresses and telephone numbers of the offices, please visit the above website or
call 2559 2297.
This guide may be freely reproduced except for advertising, endorsement or commercial
purposes. Please acknowledge the source as "A Guide to Work with Computers",
published by the Labour Department.
A Guide to Work
with Computers
1. Terms
2. Workstation design
3. Equipment
4 . Environment
5. Working posture
6. Personal factors
7. Exercises
8. Enquiries
9. Complaints
A guide to work with computers
With the rapid advancement of information technology, use of computers
is already par t of many people's daily life. Those engaged in electronic
information and computer-related professionals have to use computers for
long periods. Their regular and repetitive actions in operating their computers
may cause repetitive strain injuries and visual fatigue if they have not adopted
a proper working posture.
To avoid any involved health risk, employers and employees have to
consider their conditions and environmental factors such as lighting condition,
computer workstation design and working posture in the office.
Good communication and cooper ation between employer s and
employees is required in order to improve working conditions in relation
to safety and health at work. Any occupational health risks arising from the
use of computers will hence be reduced and work efficiency will be increased
as a result. This guide offers advice, in question and answer format, on some
commonly encountered safety and health problems in relation to computer
work with a view to assisting employers and employees to improve their
workplace conditions.
1 . Terms
What is the difference between a piece of Display Screen Equipment
(DSE), a visual display unit (VDU), a visual display terminal (VDT)
and a computer monitor?
Ans. Basically all these items refer to the same thing, i.e. a display screen
composing par t of a computer and showing characters, numbers or
2. Workstation design
Q2.1 In selecting office furniture for a computer workstation, what factors
should be considered?
Ans. The main components of a computer wor kstation are the desk or
display suppor t, suppor t for keyboard and mouse or other input device
and the chair. A wor kstation should permit the user s to adopt a
healthy, comfor table posture without overloading the musculo-skeletal
system. To achieve this aim, the furniture should be adjustable as far
as practicable. Other requirements include sufficient space on work
surfaces for documents and sufficient leg room.
A guide to work with computers
A Comfor table viewing angle, e.g. 15˚ - 20˚
B Comfor table viewing distance,
e.g. 350 - 600mm for text of normal font size
C Forearm and arm at about right angle
D Adjustable back rest
E Adjustable seat height
F Firm foot rest if required
G Adequate knee clearance
H Wrist rest if required
Screen at right angle to line of sight
Adjustable document holder
K Wrist kept straight or at most slightly inclined
L Screen suppor t adjustable for rotation and tilting
M Adjustable table height preferable
N Rounded or scrolled edge seat pad
Recommended computer workstation design and working posture
Q2.2 I want to replace the old chairs for my
Seat back width
computer operators. What are the
essential features of a suitable chair?
Ans. An office chair should have:
• a stable base (a five-pronged base
is recommended) & smooth
casters if necessar y
seat height
400-500 mm
• adjustable seat height, from 400
to 500 millimeters
• a slightly concave seatpan made
with a dense foam and a
breathable covering
400-450 mm
5 pronged base
(casters if
• swivel seat
• round or "waterfall" front edge
• adjustable backrest, both in height and tilt
• a pair of armrest with adjustable height if necessar y
Q2.3 I know that it would cause stress to the eyes if the viewing distance
is too close. What is the recommended viewing distance?
Ans. The monitor should be placed at a level where its topmost line of
display is at about or just below the operator's eye level. The viewing
distance between the operator's eyes and the screen should be around
350 to 600 millimeters for reading text of normal font size.
A guide to work with computers
Q2.4 Should I use a document holder?
If frequent viewing of document for data entr y
is required, a document holder should be used.
The document holder should be stable and
adjustable for height, distance and angle of viewing.
It can be used on either side of the monitor, thus
minimizing the need for the operator to move
the head to and fro and to refocus his eyes in
order to read the screen and the document.
Q2.5 Should I use a foot rest for my computer work?
A footrest is recommended if an operator cannot
rest his feet flatly on the floor even if the chair
height has been properly adjusted. Small sized
people usually need foot rest suppor t. The footrest
should be stable, non-slipper y, incline and height adjustable, and should
not restrict leg movement.
Q2.6 Should I use a wrist rest while keying in data?
If intensive keyboard oper ation has to be
performed, a wrist rest may be used if the user
finds it more comfor table. The primar y function
of a wrist rest is to keep the wrist straight during
keyboard use and provide padding. When a
proper wrist rest is used correctly, it can reduce the risk of repetitive
strain injuries. However, while keying, remember to keep the hands
above the keyboard and move the whole hand to reach side keys,
rather than resting the wrist on the rest and bending the wrist sideways.
The wrists should only be resting on the wrist rest during pausing.
Q2.7 How should I select a suitable wrist rest?
Ans. In selecting a wrist rest, the following
criteria should be considered:
a. thickness of the rest should be about
the same as the front of the keyboard;
b. the rest should be wide enough (front
to back) to suppor t the wrist;
Measure the distance from the top of the
space bar to the tabletop. Choose the
wrist rest to match that dimension.
c . wrist rests should not have sharp edges; and
d. made of breathable materials.
3 . Equipment
Q3.1 Some anti-glare screen suppliers claim that their anti-glare screens
can reduce radiation and prevent myopia. Is this true?
Ans. Anti-glare screens improve screen visibility by reducing bright spots
or washout caused by ambient light on monitor screens. Thus, these
screens may be used to reduce screen reflections. Radiation emitted
by a computer monitor is well below the limits set by international
bodies for limiting health risks. It is therefore not necessar y to add
any filter to reduce the emission. In any case, the anti-glare screens
are not designed for effective screening of radiation.
Currently, there is no scientific evidence that prolonged computer
work will cause permanent damage to the eyes or eyesight. However,
prolonged use of computer can lead to eye strain. The best preventive
measure to reduce eye strain is to view distant objects on a regular
basis and do eye exercises.
A guide to work with computers
Q3.2 My routine duties include answering phone call while operating the
computer. Could this be related to my neck sores?
Ans. Muscles of the neck may be sore if the phone receiver is cradled
between the head and shoulder for a long time. When a computer
and a telephone have to be used at the same time, it is recommended
for the operator to use a headset.
Q3.3 I have to use a notebook all the time and I have developed some
aches and pains in my fingers and hands. What can I do ?
Ans. The small size of the keyboard and
the pointing device of a notebook
computer lead to cramped
postures of fingers and hands, thus
causing ear ly fatigue if the
equipment is used for a prolonged
period. It is recommended that a
detachable keyboard and mouse
be used if a notebook has to be
used for long hours.
Q3.4 I have heard that a V-shaped keyboard is available. Will it do me
any good?
Ans. When operating a traditional
keyboar d, some c o mpu ter
users may have to bend their
wrists to the side to type. This
posture is unnatural and may
strain the wrists. A V-shaped
keyboard may help a user to position his hands naturally while keying
in data. If a user is working well with a traditional keyboard, he/she
may not need to change to this new type. If one wants to change to
a new design, an evaluation should be made to ensure that the users
can work comfor tably with the new keyboard.
4 . Environment
Q4.1 There are bright spots on my screen and it is difficult to see the
characters clearly. What should I do to reduce glare from the screen?
Ans. One of the main causes of eye complaint made by a computer operator
is glare. Glare can be reduced by:
a ) changing the position of any light
sources causing the glare;
b) fitting the light sources with appropriate
diffusers or lampshade;
c) providing cur tains or blinds to windows;
d) ensuring that the screen is perpendicular
to the light sources or windows;
e) using anti-glare screen only if the glare cannot be effectively
eliminated by other means.
A guide to work with computers
Q4.2 My office lighting is too bright. What is the recommended lighting
level for a computer room ?
Ans. Lighting levels ranging from 300 to 500 lux are appropriate for most
computer desk work. Generally, the maximum lighting level should not
exceed 750 lux. Excessive lighting levels have a "masking" effect and
make it difficult for the operator to see the display on the screen.
Overhead lights
(low glare shapes or louvers)
Indirect light
Task lamp
Line of sight parallel to windows
and between light fittings
Recommended lighting arrangement for a computer workstation
5 . Working posture
Q5.1 I feel aches and pains in my arms and wrists after work. Could this
be related to my working posture?
Ans. If maintained for a prolonged period of time, improper working posture
may result in pains and aches in the back, arms, neck and wrists. While
operating a computer, an operator should adopt a natural and relaxed
posture. Please refer to the diagram on page 3 for a recommended
working posture. However, even if the posture is proper, keeping it
for a long time is also stressful. Therefore, remember to change the
posture frequently or have a task break, e.g. doing alternative work.
Q5.2 Would improper mousing cause hand injury? What is the proper
way of using a mouse?
Ans. An operator should adopt the following practices in mousing:
a ) avoid squeezing the mouse or pressing the mouse buttons with
excessive force;
b) avoid bending the wrist sideways and/or forward; and
c) perform mousing and the keyboard operation at the same height.
A guide to work with computers
6 . Personal factors
Q6.1 I feel tired and have symptoms like headache and burning eyes after
working on the computer for a few hours. What should I do to take
care of my eyes?
Ans. Computer users may experience visual fatigue and discomfor t after
prolonged computer work. Symptoms include burning eyes, blurred
vision and headache. To alleviate eyestrain, a shor t task break (5 15 minutes) taken after 1 - 2 hours of continuous computer work is
recommended. During the task break, the computer user should do
alternative work, like filing, photocopying, etc., or get up, stretch and
view distant objects. Proper eye glasses should be used to correct
vision where necessar y.
Q6.2 I wear bifocal lens. Can I use it in my computer work?
Ans. Yes. A computer user who wears bifocals
tends to tilt the head back to view the
monitor through the lower close-vision
par t of the glasses. The top of the screen
should be at 50 to 100 millimeters below
eye level. If you still cannot wor k comfor tably with bifocals, you
may need another type of spectacles, e.g. a pair of monofocal glasses.
Q6.3 I am pregnant. I am concerned about the health effects of radiation
from the monitor. Can I continue my work as a computer operator?
Ans. The emission of radiation from a monitor is generally found to be
substantially below the limits set by international bodies for limiting
risk to human health. There is no conclusive scientific evidence to
indicate any adverse health effect to the operator or the foetus.
Q6.4 Can computer work trigger epileptic fits?
Ans. Most people with epilepsy are completely unaffected by computer
work. Even people suffering from the ver y rare photosensitive epilepsy,
who are susceptible to flickering lights and strip patterns, also find
computer work not affecting them in normal cases.
7 . Exercises
Q7.1 I have to use computer for a long time ever yday. Would you
recommend some simple physical exercises to relax myself during
a break?
Ans. During a break, you may follow the following recommended exercises
to relax yourself. This can prevent early fatigue and musculo-skeletal
disorders. You may repeat each exercise for several times. However,
should you really have a health complaint, you should consult a physician.
Exercises for the eyes
(1) Keep the body and the
head upright. Turn the eyes
up to look at the ceiling,
then turn down to look at
the floor.
(2) Turn the eyes left and right
slowly to look at objects
on the two sides.
(3) Turn the eyes to look at
objects at the right upper
direction and then the right
lower direction. Repeat
for the left upper and left
lower directions.
A guide to work with computers
Exercises for the neck
• Keep the arms relaxed at
your side.
• Keep the arms relaxed at
your side.
• Keep the arms relaxed at
your side.
• Bend your head forward
slightly to stretch the neck.
• Turn the head to one side
and hold for 5 seconds.
• Swing the head to the left
and hold for 5 seconds.
• Hold for 5 seconds.
• Repeat for the other side.
• Repeat for the other side.
Exercises for the
Exercises for the Exercises for the shoulders and the
upper back
upper limbs
• Raise the shoulders and
rotate backward slowly.
Repeat 10 times.
• Cross the fingers and lift
both arms up, flip the palms
upwards and stretch the
upper limbs.
• Sit upright, hold your hands
behind your head and
s t r e t c h yo u r e l b ow s
• Hold for 10 - 15 seconds.
• Force the scapulas inwards
and feel the pressure at the
upper back and the scapulas.
• Then relax the shoulders.
• Breathe deeply during the
• Hold for 5 seconds and
Exercises for the hands
(1) Stretch the fingers and hold for 10 seconds, then relax.
(2) Lift your arms to chest level with the palms facing
downwards. Slowly turn the wrists upwards and hold for
ten seconds. Slowly turn the wrists downwards and hold
for ten seconds.
8. Enquiries
If you wish to enquire about this guide or require advice on occupational
health and hygiene issues, please contact the Occupational Safety and Health
Branch of the Labour Depar tment through:
Address :
15th floor, Harbour Building, 38 Pier Road, Central, Hong Kong.
Telephone : 2852 4041
Facsimile :
2581 2049
E-mail Address:
enquir y@labour.gov.hk
Information on the ser vices provided by the Occupational Safety and
Health Council can be obtainted through its hotline 2739 9000 and website
9. Complaints
If you have any complaints about unsafe wor kplaces and practices,
please call the Labour Depar tment's Occupational Safety and Health Complaint
Hotline on 2542 2172. All complaints will be treated in the strictest confidence.
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