EN ISO 291:2005

SLOVENSKI STANDARD
01-april-2006
1DGRPHãþD
SIST EN ISO 291:1999
Polimerni materiali – Standardne atmosfere za kondicioniranje in preskušanje (ISO
291:2005)
Plastics - Standard atmospheres for conditioning and testing (ISO 291:2005)
Kunststoffe - Normalklimate für Konditionierung und Prüfung (ISO 291:2005)
Plastiques - Atmospheres normales de conditionnement et d'essai (ISO 291:2005)
Ta slovenski standard je istoveten z: EN ISO 291:2005
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
November 2005
ICS 83.080.01 Supersedes EN ISO 291:1997
English Version
Plastics - Standard atmospheres for conditioning and testing
(ISO 291:2005)
Plastiques - Atmosphères normales de conditionnement et Kunststoffe - Normalklimate für Konditionierung und
d'essai (ISO 291:2005) Prüfung (ISO 291:2005)
This European Standard was approved by CEN on 4 November 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, 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
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 291:2005: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 291:2005) 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 IBN.
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 May 2006, and conflicting national standards
shall be withdrawn at the latest by May 2006.

This document supersedes EN ISO 291:1997.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 291:2005 has been approved by CEN as EN ISO 291:2005 without any
modifications.
INTERNATIONAL ISO
STANDARD 291
Third edition
2005-11-15
Plastics — Standard atmospheres
for conditioning and testing
Plastiques — Atmosphères normales de conditionnement et d'essai

Reference number
ISO 291:2005(E)
©
ISO 2005
ISO 291:2005(E)
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ii © ISO 2005 – All rights reserved

ISO 291:2005(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 291:2005(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 third edition cancels and replaces the second edition (ISO 291:1997), which has been technically revised.
It also incorporates the Technical Corrigendum ISO 291:1997/Cor.1:1998.

iv © ISO 2005 – All rights reserved

INTERNATIONAL STANDARD ISO 291:2005(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 291:2005(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
Remarks
atmosphere
°C %
23/50 23 50 Shall be used unless otherwise
specified
27/65 27 65 May be used for tropical countries if
agreed on by all parties
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 2005 – All rights reserved

ISO 291:2005(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 ± 1 ± 5 ± 5
2 ± 2 ± 10 ± 10
NOTE Usually, the tolerances are coupled in pairs, i.e. class 1 tolerance for both temperature and relative humidity or
class 2 tolerance for both.
7 Standard and ambient temperatures
If humidity has no influence or only a negligible influence on the properties being examined, the relative
humidity does not have to be controlled. The corresponding environments are designated “temperature 23”
and “temperature 27”, respectively.
Similarly, if neither temperature nor humidity has any noticeable influence on the properties being examined,
neither the temperature nor the relative humidity has to be controlled. In this case, the atmospheric condition
is termed the “ambient temperature”.
8 Procedure
8.1 Conditioning
The period of conditioning shall be as stated in the relevant specifications for the material.
When the conditioning periods are not stated in the applicable standard, the following shall be adopted:
a) unless otherwise specified, a minimum of 88 h for atmospheres 23/50 and 27/65;
b) unless otherwise specified, a minimum of 4 h for temperatures of 18 °C to 28 °C.
N
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