EN ISO 291:2008

SLOVENSKI STANDARD
01-januar-2009
1DGRPHãþD
SIST EN ISO 291:2006
Polimerni materiali - Standardne atmosfere za kondicioniranje in preskušanje (ISO
291:2008)
Plastics - Standard atmospheres for conditioning and testing (ISO 291:2008)
Kunststoffe - Normalklimate für Konditionierung und Prüfung (ISO 291:2008)
Plastiques - Atmosphères normales de conditionnement et d'essai (ISO 291:2008)
Ta slovenski standard je istoveten z: EN ISO 291:2008
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 291
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2008
ICS 83.080.01 Supersedes EN ISO 291:2005
English Version
Plastics - Standard atmospheres for conditioning and testing
(ISO 291:2008)
Plastiques - Atmosphères normales de conditionnement et Kunststoffe - Normalklimate für Konditionierung und
d'essai (ISO 291:2008) Prüfung (ISO 291:2008)
This European Standard was approved by CEN on 21 April 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 291:2008: E
worldwide for CEN national Members.

Contents Page
Foreword.3

Foreword
This document (EN ISO 291:2008) has been prepared by Technical Committee ISO/TC 61 "Plastics" in
collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by NBN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by November 2008, and conflicting national standards shall be withdrawn
at the latest by November 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 291:2005.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 291:2008 has been approved by CEN as a EN ISO 291:2008 without any modification.

INTERNATIONAL ISO
STANDARD 291
Fourth edition
2008-05-01
Plastics — Standard atmospheres for
conditioning and testing
Plastiques — Atmosphères normales de conditionnement et d'essai

Reference number
ISO 291:2008(E)
©
ISO 2008
ISO 291:2008(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2008
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 either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2008 – All rights reserved

ISO 291:2008(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 2
5 Standard atmosphere. 2
6 Classes of standard atmosphere . 2
7 Standard and ambient temperatures . 3
8 Procedure . 3
Annex A (normative) Attainment of moisture equilibrium by plastics in a conditioning atmosphere. 4
Annex B (informative) Background information . 6
Bibliography . 8

ISO 291:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 291 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 6, Ageing, chemical
and environmental resistance.
This fourth edition cancels and replaces the third edition (ISO 291:2005), of which it constitutes a minor
revision. The main changes are as follows:
⎯ in Table 1, the way in which the two standard atmospheres are used is now described in terms of non-
tropical and tropical countries;
⎯ a second note, concerning the unacceptability of wider tolerances on temperature and relative humidity,
has been added at the end of Clause 6.

iv © ISO 2008 – All rights reserved

INTERNATIONAL STANDARD ISO 291:2008(E)

Plastics — Standard atmospheres for conditioning and testing
1 Scope
This International Standard sets out specifications relating to the conditioning and testing of all plastics and all
types of test specimen at constant atmospheric conditions.
Special atmospheres applicable to a particular test or material or simulating a particular climatic environment
are not included in this International Standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 62, Plastics — Determination of water absorption
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
standard atmosphere
preferred constant atmosphere for which specific air temperature and humidity values, as well as limit ranges
for atmospheric pressure and air-circulation velocity, are specified, the air not having any significant additional
constituents and the atmosphere not being subject to any significant additional radiation influences
NOTE 1 Standard atmospheres permit a defined state to be attained and maintained for samples or specimens.
NOTE 2 Standard atmospheres correspond to the average atmospheric conditions in laboratories and can be
established in conditioning (controlled atmosphere) cabinets, chambers or rooms.
3.2
conditioning atmosphere
constant atmosphere in which a sample or test specimen is kept before being subjected to a test
3.3
test atmosphere
constant atmosphere to which a sample or test specimen is exposed throughout a test
3.4
conditioning
one or more operations intended to bring a sample or test specimen into a state of equilibrium with regard to
temperature and humidity
3.5
conditioning procedure
combination of the conditioning atmosphere and the period of conditioning
ISO 291:2008(E)
3.6
ambient temperature
environmental conditions corresponding to the usual atmospheric conditions in laboratories with uncontrolled
temperature and humidity
NOTE The phrase “at ambient temperature” refers to an environment the air temperature of which lies within a
specified range, no consideration being given to relative humidity, atmospheric pressure or air-circulation velocity. In
general, the air-temperature range extends from 18 °C to 28 °C and is stated as “at an ambient temperature of 18 °C to
28 °C”.
4 Principle
If a test specimen is exposed to a specific conditioning atmosphere or temperature, then a reproducible state
of temperature and/or of moisture equilibrium is reached between the test specimen and the conditioning
atmosphere or temperature.
It is not the intent of this International Standard to define procedures specifying how to determine sensitivity to
moisture.
Some materials may have special conditioning requirements. Follow the relevant International Standards.
5 Standard atmosphere
Unless otherwise specified, use one of the sets of conditions given in Table 1 as the standard atmosphere.
Table 1 — Standard atmospheres
Air temperature Relative humidity (RH)
Symbol for standard
a
Remarks
atmosphere
°C %
23/50 23 50 For non-tropical countries
27/65 27 65 For tropical countries
a
When obtaining comparative data on polymers, e.g. for databases, standard atmosphere 23/50 shall be used.

NOTE The values in Table 1 apply to normal altitudes with an atmospheric pressure between 86 kPa and 106 kPa
and an air-circulation velocity u 1 m/s.
6 Classes of standard atmosphere
Table 2 gives the different classes of standard atmosphere corresponding to different tolerance levels for the
temperature and relative humidity. The tolerances given in Table 2 apply to the specimen-storage space in a
test enclosure or conditioning enclosure. Class 1 cabinets will require more frequent calibration. Follow the
manufacturer’s recommendations for calibration. Cabinets shall be calibrated at least once per year.

2 © ISO 2008 – All rights reserved

ISO 291:2008(E)
Table 2 — Standard atmosphere classes corresponding to different permitted deviations
Permitted deviations in relative humidity (RH)
Permitted deviations in
temperature
Class
%
°C
23/50 27/65
± 1 ± 5 ± 5
2 ± 2 ± 10 ± 10
NOTE 1 Usually, the tolerances are coupled in pairs, i.e. class 1 tolerance for both temperature and relative humidity or
class 2 tolera
...