ISO 291:2008 pdf free.Plastics — Standard atmospheres for conditioning and testing.
ISO 291:2008 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.
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
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.
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.ISO 291:2008 pdf free download.