Microbial Ranking of Porous Packaging Materials ASTM F1608

Microbial Ranking of Porous Packaging Materials ASTM F1608

ASTM F1608 is used to determine the Microbial Ranking of Porous Packaging Materials by Exposure Chamber Method. The Exposure Chamber Method is used to measure the ability of packaging materials to stop bacteria from invading the packaging of sterile medical devices.


    In ASTM F1608, the Exposure Chamber Method determines the ability of porous packaging material to stop microbes from contaminating the contents. It assesses the relative potential of a particular porous material to contribute to the loss of sterility of the contents.

    Exposure Chamber Method alone cannot predict the sterility of contents because that depends upon several factors apart from the microbial ranking of a porous packaging material:

    The bacterial challenge (number and kinds of microorganisms) that the package will encounter in its distribution
    The microstructure of a porous material
    The package design, such as the presence of secondary and tertiary packaging, and
    The nature of the device within the package.

    Porous packaging material stops microbes from entering medical packaging and allows sufficient airflow needed for sterilization through a gas.

    Test Procedure:

    In ASTM F1608, An aerosol of bacterial spores is sprayed on the porous packaging material inside the exposure chamber. Spores that pass through the material are collected on membrane filters and counted. The Log-reduction value (LRV), the ability of a packaging material to stop microorganisms, is calculated by comparing the logarithm of the number of spores passing through the porous material with the logarithm of the bacterial challenge.

    The Exposure Chamber Method is conducted in a microbiological laboratory by trained personnel, using all the standard equipment and supplies needed to conduct such microbiological manipulation.

     Specimen size:

    Five disk shaped samples of diameter 47 or 50 mm are cut using a disk cutter and used for the test. The minimum number of samples for a particular material is two; however, higher numbers of samples increase the accuracy of the test. 


    Log-reduction value (LRV) is calculated by the following equation:

    LRV = log10N0 – log10 N₁

    N0 = average bacterial challenge determined from the challenge control filter.

    N₁ = average number of bacteria passing through.


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