ISO 8995-1:2002

INTERNATIONAL ISO
STANDARD
CIE S 008/E
Second edition
2002-05-15
Lighting of indoor work places
Éclairage intérieur pour des lieux de travail

Reference number
ISO 8995:2002(E)
CIE S 008/E-2001
©
ISO 2002
ISO 8995:2002(E)
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ISO 8995:2002(E)
Foreword
ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas
therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission(IEC)onallmattersofelectrotechnicalstandardization.
International Standard ISO 8995 was prepared as Standard CIE S 008/E by the International Commission on
Illumination, which has been recognized by the ISO Council as an international standardizing body. It was adopted
by ISO under a special procedure which requires approval by at least 75 % of the member bodies casting a vote,
and is published as a joint ISO/CIE edition.
The International Commission on Illumination (abbreviated as CIE from its French title) is an organization devoted
to international cooperation and exchange of information among its member countries on all matters relating to the
science and art of lighting.
AttentionisdrawntothepossibilitythatsomeoftheelementsofthisInternationalStandardmaybethesubjectof
patentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.
InternationalStandardISO8995waspreparedjointlybyErCgoIEnomTiCcs3-,S21ubcanomdmIiSOttee/TC159,
SC5,Ergonomics of the physical environment.
This second edition cancels and replaces the first edition (ISO8995:1989), of which it constitutes a technical
revision.
ISO 8995:2002(E)
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iv ©ISO2002–Allrightsreserved
ISO 8995:2002(E)
CIE S 008/E-2001
Standard
Lighting of Indoor Work Places
Eclairage intérieur pour des lieux de travail
Beleuchtung von Arbeitsplätzen in Innenräumen
CIE Standards are copyrighted and shall not be reproduced in any form, entirely or partly, without
the explicit agreement of the CIE.
CIE Central Bureau, Vienna S 008/E

Kegelgasse 27, A-1030 Vienna, Austria

UDC: 628.972 Descriptor: Interior lighting
v
ISO 8995:2002(E)
CIE S 008/E-2001
 CIE 2001
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from CIE Central Bureau at the address below.
CIE Central Bureau
Kegelgasse 27
A-1030 Vienna
Austria
Tel.: +43 1 714 3187 0
Fax: +43 1 713 0838 18
e-mail: ciecb@ping.at
Web: www.cie.co.at/cie
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ISO 8995:2002(E)
CIE S 008/E-2001
Foreword
Standards produced by the Commission Internationale de lÉ’clairage (CIE) are a concise
documentation of data defining aspects of light and lighting, for which international harmony
requires such unique definition. CIE Standards are therefore a primary source of
internationally accepted and agreed data, which can be taken, essentially unaltered, into
universal standard systems.
This International Standard was prepared jointly CbIEy -TC 3-21 and ISO/TC 159/SC 5.
It replaces publication CIE 29.2-1986 and deals with Lighting Requirements for Indoor Work
Places.
Table of contents
FOREWORD . III
INTRODUCTION . 1
1. SCOPE. 1
2. NORMATIVE REFERENCES. 1
3. DEFINITIONS . 2
4. LIGHTING DESIGN CRITERIA . 2
4.1 Luminous environment. 2
4.2 Luminance distribution. 3
4.3 Illuminance. 3
4.3.1 Recommended illuminances at the task area . 3
4.3.2 Scale of illuminance. . 4
4.3.3 Illuminances of immediate surroundings . 4
4.3.4 Uniformity . 4
4.4 Glare. 5
4.4.1 Shielding against glare. 5
4.4.2 Discomfort glare. 5
4.4.3 Veiling reflections and reflected glare. 6
4.5 Directionality . 6
4.5.1 Modelling . 6
4.5.2 Directional lighting of visual tasks. 6
4.6 Colour aspects. 6
4.6.1 Colour appearance. 7
4.6.2 Colour rendering . 7
4.7 Daylight. 7
4.8 Maintenance . 8
4.9 Energy considerations. 8
4.10 Lighting of workstations with visual display terminals VDT . 8
4.11 Flicker and stroboscopic effect. 8
4.12 Emergency lighting. 9
5. SCHEDULE OF LIGHTING REQUIREMENTS. 9
6. VERIFICATION PROCEDURES . 17
6.1 Illuminance. 17
6.2 Unified glare rating. 17
6.3 Colour rendering index (R ). 17
a
6.4 Colour appearance (T ). 17
cp
6.5 Maintenance . 17
6.6 Luminaire luminance. 17
6.7 Tolerances in measurements. 18
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ISO 8995:2002(E)
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LIGHTING OF INDOOR WORK PLACES
Introduction
Good lighting will create a visual environment that enables people to see, to move about
safely and to perform visual tasks efficiently, accurately and safely without causing undue
visual fatigue and discomfort. The illumination may be daylight, electric light or combination of
both.
Good lighting requires equal attention to the quantity and quality of the lighting. While
the provision of sufficient illuminance on the task is necessary, in many instances the visibility
depends on the way in which the light is delivered, the colour characteristics of the light
source and surfaces together with the level of glare from the system. In this standard
opportunity was taken to specify for various work places and task types not just the
illuminance but also the limiting discomfort glare and minimum colour rendering index of the
source. Parameters to create comfortable visual conditions are proposed in the body of this
standard. The recommended values are considered to represent a reasonable balance,
having regard to the requirements for safe, healthy and efficient work performance. The
values can be achieved with practical energy efficient solutions.
There are also visual ergonomic parameters such as perceptual ability and the
characteristics and attributes of the task, which determine the quality of the operator’s visual
skills, and hence performance levels. In some cases enhancement of these influencing factors
can improve performance without the need to raise illuminance. For example by improving the
contrast of the task attributes, enlarging the task by the use of up to date visual aids (glasses)
and by the provision of special lighting systems with local directional lighting capability.
1. Scope
This standard specifies lighting requirements for indoor work places and for people to perform
the visual tasks efficiently, in comfort and safety throughout the whole work period.
This standard does not explain how lighting systems or techniques should be
designed to optimise solutions for specific work places. These may be found in the relevant
CIE guides and reports.
2. Normative references
The following standards contain provisions which, through reference in this text, constitute
provisions of this International Standard. At the time of publication, the editions indicated were
valid. All standards are subject to revision, and parties to agreements based on this Standard
are encouraged to investigate the possibility of applying most recent editions of the standards
indicated below. Members of CIE, the International Electrotechnical Commission (IEC) and the
International Organization for Standardization (ISO) maintain registers of currently valid
international standards.
ISO 3864 Safety colours and safety signs
ISO 6309 Fire protection - safety signs
ISO 6385 Ergonomic principles in the design of work systems
ISO 9241 Parts 6/7/8 Ergonomic requirements for office work with visual display
terminals
CIE 13.3 - 1995 Method of measuring and specifying colour rendering of light
sources
CIE 16 - 1970 Daylight
CIE 17.4 - 1987 International lighting vocabulary 4th ed. – equivalent to IEC
50(845)
CIE 19.2 - 1981 An analytic model for describing the influence of lighting
parameters upon visual performance
CIE 40 - 1978 Calculations for interior lighting - basic method
CIE 58 - 1983 Lighting for sports halls
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CIE 60 - 1984 Vision and the visual display unit work station
CIE 62 - 1984 Lighting for swimming pools
CIE 96 - 1992 Electric light sources. State of the art - 1991
CIE 97 - 1992 Maintenance of indoor electric lighting systems
CIE 103/5 - 1993 The economics of interior lighting maintenance
CIE 117 - 1995 Discomfort glare in interior lighting
CIE 129 - 1998 Guide for lighting of exterior work areas
3. Definitions
In general the terms used in this standard are defined in the CIE Lighting Vocabulary
(CIE 17.4 – 1987), but there are few more terms that are defined below:
3.1 visual task: The visual elements of the task to be carried out.
3.2 task area: The partial area in the work place in which the visual task is located and
carried out.
3.3 immediate surrounding: A zone of at least 0,5 m width surrounding the task area
within the field of vision.
3.4 maintained illuminance ( E ): Value below which the average illuminance on the
m
specified surface should not fall.
3.5 unified glare rating (UGR): The CIE discomfort glare measure.
3.6 limiting unified glare rating (UGR ): The maximum allowable design UGR value for
L
the lighting installation.
3.7 Shielding angle: the angle measured from the horizontal, down to which the lamp(s)
is screened by the luminaire from direct view by an observer.
3.8 Working plane: the reference surface defined as the plane at which work is usually
done.
4. Lighting design criteria
4.1 Luminous environment
Good lighting practice for work places is more than just providing good task visibility. It is
essential that tasks are performed easily and in comfort. Thus the lighting must satisfy the
quantitative and qualitative aspects demanded by the environment. In general lighting is to
ensure:
- visual comfort, where the workers have a feeling of well-being,
- visual performance, where the workers are able to perform their visual tasks,
speedily and accurately even under difficult circumstances and during long
periods,
- visual safety, to see one’s way around and detect hazards.
To satisfy these, attention to all parameters contributing to the luminous environment
is required.
The main parameters are:
- luminance distribution,
- illuminance,
-glare,
- directionality of light,
- colour aspect of the light and surfaces,
- flicker,
- daylight,
- maintenance.
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Design values for the quantifiable parameters of illuminance, discomfort glare and
colour rendering are given in clause 5 for the various activities.
Note: In addition to the lighting there are other visual ergonomic parameters which
influence operators visual performance, such as:
a) the intrinsic task properties (size, shape, position, colour and reflectance of
detail and background)
b) ophthalmic capacity of the operator (visual acuity, depth perception, colour
perception).
Attention to these factors can enhance visual performance without the need for
higher illuminance.
4.2 Luminance distribution
The luminance distribution in the field of view controls the adaptation level of the eyes, which
affects task visibility.
A well balanced adaptation luminance is needed to increase:
- visual acuity (sharpness of vision),
- contrast sensitivity (discrimination of relatively small luminance differences),
- efficiency of the ocular functions (such as accommodation, convergence, pupillary
contraction, eye movements, etc.).
Diverse luminance distribution in the field of view also affects visual comfort and
should be avoided:
- too high luminances can give rise to glare.
- too high luminance contrasts will cause visual fatigue due to continuous
readaptation of the eyes.
- too low luminances and too low luminance contrasts result in a dull and non-
stimulating working environment.
- attention should be given to adaptation in moving from zone to zone within a
building.
The luminances of all surfaces are important and will be determined by the reflectance
of and the illuminance on the surfaces. The range of useful reflectances for the major interior
surfaces are:
- ceiling: 0,6 - 0,9
- walls: 0,3 - 0,8
- working planes: 0,2 - 0,6
- floor: 0,1 - 0,5
4.3 Illuminance
The illuminance and its distribution on the task areas and the surrounding area have a major
impact on how quickly, safely and comfortably a person perceives and carries out the visual
task. For spaces where the specific area is unknown the area where the task may occur is
taken as the task area.
All values of illuminances specified in this standard are maintained illuminances and
will provide for visual safety at work and visual performance needs.
4.3.1 Recommended illuminances at the task area
The values given in clause 5 are the maintained illuminances over the task area on the
reference surface which may be horizontal, vertical or inclined. The average illuminance for
each task shall not fall below the values given in clause 5 regardless of the age and condition
of the installation. The values are valid for normal visual conditions and take into account the
following factors:
- requirements for visual tasks,
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- safety,
- psycho-physiological aspects such as visual comfort and well-being,
- economy,
- practical experience.
The value of illuminance may be adjusted, by at least one step on the scale of
illuminance, if the visual conditions differ from the normal assumptions. The illuminance
should be increased when:
- unusually low contrasts are present in the task,
- visual work is critical,
- errors are costly to rectify,
- accuracy or higher productivity is of great importance,
- the visual capacity of the worker is below normal.
The required maintained illuminance may be decreased when:
- the details are of an unusually large size or high contrast,
- the task is undertaken for an unusually short time.
In areas where continuous work is carried out the maintained illuminance shall not be
less than 200 lux.
4.3.2 Scale of illuminance
A factor of approximately 1,5 represents the smallest significant difference in subjective effect
of illuminance. In normal lighting conditions approximately 20 lux of horizontal illuminance is
required to just discern features of the human face and is the lowest value taken for the scale
of illuminances. The recommended scale of illuminance is:
20 - 30 - 50 - 75 - 100 - 150 - 200 - 300 - 500 - 750 - 1000 - 1500 - 2000 - 3000 - 5000 lux.
4.3.3 Illuminances of immediate surroundings
The illuminance of immediate surrounding areas shall be related to the illuminance of the task
area and should provide a well-balanced luminance distribution in the field of view.
Rapid spatial changes in illuminances around the task area may lead to visual stress
and discomfort.
The maintained illuminance of the immediate surrounding areas may be lower than
the task illuminance but shall not be less than the values given in the table below.
Task illuminance Illuminance of immediate surroundings
lux lux
> 750 500
500 300
300 200
< 200 Same as task illuminance
In addition to the task illuminance the lighting shall provide adequate adaptation
luminance in accordance with clause 4.2.
4.3.4 Uniformity
The uniformity of the illuminance is the ratio of the minimum to average value. The
illuminance shall change gradually. The task area shall be illuminated as uniformly as possible.
The uniformity of the task illuminance shall not be less than 0,7. The uniformity of the
illuminance of the immediate surrounding areas shall be not less than 0,5.
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4.4 Glare
Glare is the visual sensation produced by bright areas within the field of view and may be
experienced either as discomfort glare or disability glare. Glare may also be caused by
reflections in specular surfaces usually known as veiling reflections or reflected glare.
It is important to limit the glare to avoid errors, fatigue and accidents.
Disability glare is more common in exterior lighting but may also be experienced from
spotlights or large bright sources such as a window in a relatively poorly lit space.
In interior workplaces discomfort glare usually arises directly from bright luminaires or
windows. If the discomfort glare limits are met then disability glare is not usually a major
problem.
4.4.1 Shielding against glare
Glare is caused by excessive luminances or contrasts in the field of view and can impair the
vision of objects. It should be avoided for example by suitable shielding of lamps or shading of
windows by blinds.
For electric lamps the minimum shielding angle for lamp luminances shall be not less
than the values given in the table below:
Lamp luminance
Minimum shielding angle
kcd/m
1 to 20 10°
20 to 50 15°
50 to 500 20 °
> 500 30°
The above mentioned shielding angle should not be applied to luminaires which do
not appear in the field of view of a worker during usual work and/or do not give the worker any
noticeable disability glare.
4.4.2 Discomfort glare
The discomfort glare rating of the lighting installation shall be determined by the CIE Unified
Glare Rating (UGR) tabular method, based on formula:
 
0,25 L ⋅ ω
 
UGR = 8 ⋅ log ⋅
∑
 
L
p
b
 
where
- L is the background luminance (cd/m ),
b
- L is the luminance of the luminous parts of each luminaire in the direction of the
observer’s eye (cd/m ),
- ω is the solid angle of the luminous parts of each luminaire at the observer’s eye
(steradian),
- p is the Guth position index for each individual luminaire which relates to its
displacement from the line of sight.
Details of the UGR method are given in CIE 117 - 1995.
In this standard all UGR values in clause 5 are based on the standard observer’s
position which have been validated by the UGR tabular method at a 1:1 spacing to height
ratio. The UGR data shall be corrected for the initial luminous flux of the lamps used. If the
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lighting installation is composed of different types of luminaires with different photometry
and/or lamps, the determination of the UGR value shall be applied to every lamp/luminaire
combination in the installation. The highest UGR value thus obtained shall be taken as typical
value of the entire installation and shall conform to the UGR limit. All assumptions made in the
determination of UGR shall be stated in the scheme documentation.
The UGR value of the lighting installation shall not exceed the value given in clause 5.
Note: The variations of UGR within the room may be determined using the tabular
method or the formula for different observer positions.
The values of UGR limits in clause 5 were taken from the UGR scale - where each
step in the scale represents one significant change in glare effect and 13 represents the least
perceptible discomfort glare.
The UGR scale is: 13 - 16 - 19 - 22 - 25 - 28
4.4.3 Veiling reflections and reflected glare
Specular reflections in the visual task, often called veiling reflection or reflected glare, may
alter task visibility, usually detrimentally. Veiling reflections and reflected glare may be
prevented or reduced by the following measures:
- arrangement of luminaires and work places (avoid placing luminaires in the
offending zone),
- surface finish (use low gloss surface materials),
- luminance of luminaires (limit),
- increased luminous area of luminaire (enlarge luminous area),
- ceiling and wall surfaces (lighten, avoid bright spots).
4.5 Directionality
Directional lighting may be used to highlight objects, to reveal texture and improve
appearance of people within the space. This is described by the term “modelling”. Directional
lighting of a visual task may also enhance its visibility.
4.5.1 Modelling
Modelling refers to the balance between diffuse and directional light. It is a valid criterion of
lighting quality in virtually all types of interiors. The general appearance of an interior is
enhanced when its structural features, the people and objects within it are lit so that form and
texture are revealed clearly and pleasingly. This occurs when the light comes noticeably from
one direction; the shadows formed are essential to good modelling and are formed without
confusion.
The lighting should not be too directional as it can produce harsh shadows, neither
should it be too diffuse or the modelling effect will be lost entirely, resulting in a very dull
luminous environment.
4.5.2 Directional lighting of visual tasks
Lighting from a specific direction can reveal details within a visual task, increasing their
visibility and making the task easier to perform. Particularly important for fine textured tasks
and scribes/grooves.
4.6 Colour aspects
The colour qualities of a near-white lamp are characterised by two attributes:
- the colour appearance of the lamp itself,
- its colour rendering capabilities, which affect the colour appearance of objects
and persons illuminated by the lamp.
These two attributes must be considered separately.
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ISO 8995:2002(E)
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4.6.1 Colour appearance
The “colour appearance” of a lamp refers to the apparent colour (lamp chromaticity) of the
light it emits. It may be described by its correlated colour temperature.
Lamps are usually divided into three groups according to their correlated colour
temperature (T ).
cp
Colour appearance Correlated colour temperature
warm below 3300 K
intermediate 3300 K to 5300 K
cool above 5300 K
The choice of colour appearance is a matter of psychology, aesthetics and of what is
considered to be natural. The choice depends on illuminance, colours of the room and
furniture, surrounding climate and the application. In warm climates generally a cooler light
colour appearance is preferred, and in cold climates a warmer light colour appearance is
preferred.
4.6.2 Colour rendering
It is important for both visual performance and the feeling of comfort and well
...