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IS0
I N T ERN AT I O NA L O RG A N IIAT I O N FOR STAN DA R D IZ AT I O N
IS0 RECOMMENDATION
R 557
SYMBOLS, DIMENSIONS AND LAYOUT
FOR SAFETY SIGNS
1st EDITION
March 1967
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized herefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 557, Symbols, Dimensions and Layout for Safety Signs,
was drawn up by Technical Committee ISO/TC 80, Safety Colours, the Secretariat of which
is held by the Nederlands Normalisatie-instituut ("1).
1956 and led, in 1963, to
Work on this question by the Technical Committee began in
a Draft IS0 Recommendation.
the adoption of
In July 1964, this Draft IS0 Recommendation (No. 734) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifkations of an
editorial nature, by the following Member Bodies :
Italy Sweden
Canada
Chile Korea, Rep. of Switzerland
Czechoslovakia Morocco Turkey
Denmark Netherlands U.A.R.
New Zealand United Kingdom
Germ an y
Norway U.S.S.R.
Greece
Hungary Portugal Yugoslavia
Israel Republic of South Africa
Three Member Bodies opposed the approval of the Draft:
Belgium
France
India
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in March 1967, to accept it as an IS0 RECOMMENDATION.
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IS0 / R 557 - 1961 (E)
I IS0 Recommendation R 557 March 1967
SYMBOLS, DIMENSIONS AND LAYOUT
FOR SAFETY SIGNS
1. SCOPE
This IS0 Recommendation applies to
(U) the dimensions of safety signs in geometric forms as given in IS0 Recommendation
R 408, Safety Colours;
(b) symbolic images to be placed on those safety signs, representing the objects or events
to which the safety signs are intended to call particular attention;
(c) the layout of the signs.
2. DEFINITIONS
The following terms are used for notions applied in this IS0 Recommendation:
I
contrast colour-neutral colour, or white or black, used as a contrast in combination with
the safety colour or with the auxiliary colour;
safety symbol-simple image graphically specifying more closely the meaning of the safety
L
indication ;
safety sign-geometric form (e.g. circle, triangle or rectangle) containing a safety symbol,
wording or both.
3. PURPOSE OF SAFETY SIGNS
I
The purpose of the safety signs and of the symbols which may appear on them, together with
the application of the safety colours which may reinforce their effect, is to attract attention
rapidly to a danger and to facilitate its identification by specifying it, if necessary, by means of
more precise indications.
They may also be used for indicating the location of devices and equipment which are particularly
important from the safety point of view. Safety signs and symbols do not by themselves eliminate
any danger, and the instructions or warnings they give cannot be substituted for proper accident
prevention measures.
4. OVERALL DIMENSIONS OF SAFETY SIGNS
I
The overall dimensions of safety signs should be such that the area S of a safety sign and the
distance of observation L comply with the formula
L=
S>-
2000
S and L being expressed in the same unit of measurement (e.g. the metre).
5. SYMBOLS
The dimensions of essential details of safety symbols should be in the ratio of at least l/lOOO of
the distance of observation, corresponding approximately to a visual angle of 3' 30" (in com-
pliance with the following rule: the dimensions of essential details of the symbols should be at
least 3 % of the maximum dimension of the safety sign).
This rule is sufficient for the observation of the essential details under the following conditions
recommended in general for the use of safety signs:
- illuminance level not less than 50 lux on the surface of the sign,
- luminance contrast A within the sign, not less than 25 %, where A is the difference
between the luminance level of the safety colour and that of the
contrast colour divided by the higher of the two.
When the minimum illuminance level of 50 lux is not attained by the ordinary lighting, users are
recommended to arrange for special lighting on the signs. In a number of cases, it may be of
advantage to make use of luminescent or retro-reflective signs.
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IS0 / R 557 - 1967 (E)
The design of symbols should be as simple as possible and details not essential for the identifica-
tion of the symbols should be omitted. A representation of a flame, for example, should contain
only those details that are strictly necessary so that there can be no doubt as to its identification
as a flame.
It is also recommended that the use of macabre or horrifying designs for the symbols
...