Calculation of the microbial challenge during transport and storage


Since the sterility of a product cannot be confirmed with a non-destructive test before its application in patients, special techniques of quality assurance are required. In addition to the visual inspection of failures such as punctures, tears etc. it is necessary to consider other possible factors that impair sterility during transport and storage. An important factor ist the microbial challenge as a result of environmental air flow through the porous component of packaging. In the computer program, relevant parameters such as microbial content of the air, changes in temperature and air pressure as well as the volume of the packaging are entered in order to assess the microbial challenge. The required barrier effectiveness of the packaging will then be determined considering the sterility assurance level (SAL) of 1 : 1,000,000.

Explanations of the calculation

Click on "Run program" in the left frame.  If you want to leave the program, click the blue link "go back".

The microbial challenge to the packaging from environmental factors can be calculated with our computer program. One important step consists of determining the volume of air that passes through the porous components of the packaging during transport and storage. Physical factors (chiefly meteorological changes in air pressure, transport to locations at different altitudes and changes in temperature) lead to an exchange of air between the inside of the packaging and the surroundings. The estimated gaseous volume enclosed by the packaging is required for this calculation. In terms of physics, the volume flow of air into the packaging accords with the Boyle-Mariotte law "p x V = constant" when air pressure changes are effective. According to the first Gay-Lussac law, the temperature-dependent volume change is determined for the isobaric states using the thermal volume-expansion coefficient. The determined or estimated airborne microbial concentration is also required. The total microbial content in the potentially penetrating air volume determined with this procedure is the microbial challenge of the packaging. This is expressed as the decimal logarithmic microbe count. The sterility assurance level (SAL)  of 1 : 1,000,000 is taken into consideration in addition to the concrete microbial challenge in order to attain the value for the required barrier effectiveness. In the program, this is specified as the required logarithmic reduction value (LRV) and required filtration efficiency (%).