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Ref. NO.: ISO/R 291 - 1963 (E)
IS0
INTERN AT I ON AL ORGAN I ZATl O N FOR STA N DA RD IZATl O N
IS0 RECOMMENDATION
R 291
PLASTICS
STANDARD ATMOSPHERES FOR CONDITIONING AND TESTING
1st EDITION
February 1963
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore 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 291, Plastics - Standard Atmospheres for Conditioning and
Testing, was drawn up by Technical Committee ISO/TC 61, Plastics, the Secretariat of which is
held by the American Standards Association, Inc. (ASA).
Work on this question by the Technical Committee began in 1951 and led, in 1958, to the
adoption of a Draft IS0 Recommendation.
In October 1959, this Draft IS0 Recommendation (No. 316) was circulated to all the IS0
Member Bodies for enquiry. It was approved by the following Member Bodies:
Argentina Germany Poland
Australia Hungary Portugal
Austria India Romania
Belgium Israel Spain
Burma Italy Sweden
Chile Japan Switzerland
Czechoslovakia Mexico United Kingdom
France Net herlands U.S.A.
U.S.S.R.
No Member Body opposed the approval of the Draft.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Coun-
cil, which decided, in February 1963, to accept it as an IS0 RECOMMENDATION.
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ISO/R 291 - 1963 (E)
IS0 Recommendation R 291 February 1963
PLASTICS
STANDARD ATMOSPHERES FOR CONDITIONING AND TESTING
1. SCOPE
This IS0 Recommendation applies to the normal conditioning and testing of all plastics materials
and all types of test specimens under approximately ambient atmospheric conditions. Special
atmospheres applicable to a particular test or material or simulating a particular climatic environ-
ment are not included.
2. DEFINITION
Conditioning, for the purposes of this IS0 Recommendation, means exposure of plastics materials
to the influence of a prescribed atmosphere for a stipulated period of time. In this sense, the
principle aim of conditioning is to improve the reproducibility of test results.
3. STANDARD ATMOSPHERE
The standard test atmosphere should be chosen among those defined below:
3.1 For use when control of temperature and humidity is necessary:
(I) 20 "C 65 per cent relativ
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