| Your are encouraged to print this page and use
the information to determine appropriate illuminance levels. INDOOR ILLUMINANCE LEVEL RECOMMENDATIONS
This procedure is the currently recognized method of the
Illuminating Engineering Society of North America to determine the level of maintained
illumination needed to perform a specific task. This method considers factors that most
commonly contribute to the visual comfort of the various task listed later in this
article. It provides a range of illumination levels for defined task, then specifies
a target luminance level from within that range using factors determined through
research of lighting performance requirements.
The following conditions are factored into
this method:
- Task to be performed.
- Detail of the objects to be viewed.
- Age of the Observer
- Importance of speed and accuracy for the visual task
- Reflectance of the background material.
Determining Appropriate Illuminance Levels
Step 1 Determine the type of activity for which the level
of lighting is to be selected.
Step 2 Select the appropriate
illuminance category by
one of the following methods.
When the visual task is defined by one of the typical task
categories, choose the appropriate illuminance category from Table A
SPECIFIC TASK ILLUMINANCE LEVEL GUIDE
Table A |
Type
of Activity |
Illuminance Category or fc Level |
Type
of Activity |
Illuminance Category or fc Level |
Type
of Activity |
Illuminance Category or fc Level |
Auditoriums |
Banks |
Merchandising Spaces |
Assembly |
C |
Lobby-general |
C |
Circulation |
30 |
Social
Activity |
C |
Writing
area |
D |
High
activity |
30 |
Aircraft Maintenance |
Teller's
stations |
E |
Medium
activity |
20 |
General |
75 |
Breweries |
D |
Low
activity |
10 |
Electrical,
auto |
150 |
Canning and Preserving |
Merchandising |
Upholstery |
100 |
Continuous-belt
sanding |
E |
High
activity |
115 |
Parts
Inspection |
100 |
Sink
canning |
E |
Medium
activity |
100 |
Paint
Shop |
100 |
Hand
packing |
D |
Low
activity |
30 |
Aircraft Manufacturing |
Inspection |
F |
Offices |
Rough
bench work |
50 |
Clothing Product |
Offices
(see reading) |
C |
Drilling,
riveting, screw |
75 |
Cutting
and sewing |
G |
Lobbies,
lounges |
C |
Medium
bench work |
100 |
Pressing |
F |
Reception
areas |
C |
Final
assembly |
100 |
Conference Rooms |
Reading |
Assembly |
Conferring |
D |
Xerography,
mimeograph |
D |
Simple |
D |
Corridors |
C |
Computer
screens |
D |
Moderately
difficult |
E |
Corridors |
B |
#3
pencil and softer leads |
E |
Difficult |
F |
Drafting |
#4
pencil and harder leads |
F |
Very
Difficult |
G |
Muylar,
vellum or tracing |
E |
Ball-point
pen |
D |
Audiovisual Areas |
D |
Low
Contrast |
F |
8
and 10 point type |
D |
Automobile Manufacturing |
Blueprints |
E |
Glossy
magazines |
D |
Frame
assembly |
50 |
Exhibition Halls |
C |
Newsprint |
D |
Chassis
assembly |
100 |
Libraries |
Schools |
Final
assembly |
200 |
Reading
areas |
D |
Classrooms
(see reading) |
E |
Bakeries |
D |
|
|
Science
Laboratories |
E |
|
Stairwells |
C |
If a specific task cannot be established, the illuminance
category may be determined from the generic task description listed in Table B.
RANGE OF ILLUMINANCES
Table B |
Type of Activity |
Illuminance Category |
Lux |
Foot-candles |
Reference Work Plane |
Public
spaces with dark surroundings |
A |
20
- 30 - 50 |
2
- 3 - 5 |
|
Simple
orientation for short temporary visits |
B |
50
- 75 - 100 |
5
- 7.5 - 10 |
General
Lighting throughout spaces |
Working
spaces where visual tasks are only occasionally performed |
C |
100
- 150 - 200 |
10
- 15 - 20 |
|
Performance
of visual task of high contrast or large size |
D |
200
- 300 - 500 |
20
- 35 - 50 |
|
Performance
of visual task of medium contrast or small size |
E |
500
- 750 - 1000 |
50
- 75 - 100 |
Illuminance
on task |
Performance
of visual task of low contrast or very small size over |
F |
1000
- 1500 - 2000 |
100
- 150 - 200 |
|
Performance
of visual task of low contrast or very small size over a prolonged period |
G |
2000
- 3000 - 5000 |
200
- 300 - 500 |
Illuminance
on task obtained by a combination of general and task lighting |
Step 3 Establish illuminance target value. Once the
illuminance category is chosen, an exact illuminance level may be determined from within
this range. These levels are established on Table C by matching the appropriate
user, room, and task characteristics with the previously determined illuminance category.
ILLUMINANCE VALUES
Table C |
A) General Lighting Throughout Room |
Factors |
Illuminance Categories |
Average Age of Occupants |
Average Reflectance of Room Surface |
A |
B |
C |
Under 40 |
Over 70 |
2 |
5 |
10 |
30-70 |
2 |
5 |
10 |
Under 30 |
2 |
5 |
10 |
40-55 |
Over 70 |
2 |
5 |
10 |
30-70 |
3 |
7 |
15 |
Under 30 |
5 |
10 |
20 |
Over 55 |
Over 70 |
3 |
7 |
15 |
30-70 |
5 |
10 |
20 |
Under 30 |
5 |
10 |
20 |
B) Illuminance on Task |
Factors |
Illuminance Categories |
Average
Age of Occupants |
Demand
for speed and/or accuracy |
Average
Reflectance of Room Surface |
D |
E |
F |
G |
Under 40 |
Not Important |
Over
70 |
20 |
50 |
100 |
200 |
30-70 |
20 |
50 |
100 |
200 |
Under
30 |
30 |
75 |
150 |
300 |
Important |
Over
70 |
20 |
50 |
100 |
200 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
30 |
75 |
150 |
300 |
Critical |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
30 |
75 |
150 |
300 |
40-55 |
Not Important |
Over
70 |
20 |
50 |
100 |
200 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
30 |
75 |
150 |
300 |
Important |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
30 |
75 |
150 |
300 |
Critical |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
50 |
100 |
200 |
500 |
Over 55 |
Not Important |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
30 |
75 |
150 |
300 |
Important |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
30 |
75 |
150 |
300 |
Under
30 |
50 |
100 |
200 |
500 |
Critical |
Over
70 |
30 |
75 |
150 |
300 |
30-70 |
50 |
100 |
200 |
500 |
Under
30 |
50 |
100 |
200 |
500 |
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