Method

When creating the thermal profile for a dry heat sterilization process, the main tests to be performed are heat penetration and heat distribution. The former is concerned with the heat generation inside the vessel and it’s homogeneity and the later is focused on the heat transmitting from the vessel to the product and its effectiveness. This is normally measured in terms of lethality. The worst-case scenario is a recommended perspective as an acceptance criterion.

Data collection
Independent on the technique used for depyrogenation, static or dynamic, it is important to record simultaneous temperature data from a relevant number of points. In the case of a batch set-up it is recommended to use at least three points, but in the case of large vessels a larger number is recommended. For sterilization tunnels, a three-line set up is the most common way to place the sensors; one at the beginning of the batch, on in the middle and one at the end of the batch. The number of sensors per line is dependent on the width of the transport band. Creating and documenting sensor positioning is an important part of the documentation for the process control. Using the Unit tool inside the ValSuite™ software makes it possible to have a documented map of sensor placement that will facilitate repeatable and comparable studies.

Once the position of the sensors in the vessel has been documented, it is necessary to observe sensor placement inside the product. With the help of semi-flex metal sensors is possible to accurately locate the sensing element in the cold spot. It is important to take into account the kind of heat convection used in the vessel and the shape of the product for the correct assessment of the cold spot. ValSuite™ software facilitates the documentation of sensor placement in the cold spot by allowing users to include descriptive pictures per every channel used.

Data analysis
When all data is collected, the user must observe the homogeneity, stability and heat generation of the vessel, in order to create a good assessment of the heat distribution during all the phases of the process. Valsuite™ provides tools to analyze the performance of the vessel in all phases of the process. The use of time-markers helps to generate graphical and analytical reference points in the data collected. Statistics such as min. max, delta and Lethality Fh are also available in the software. Valsuite™ software integrates all calculations into self-generated reports without the need to export data into other software. Reports can also include the placement of the loggers inside the vessel and descriptive pictures of sensor positioning. Generating ValSuite™ reports provides the highest data security for the results, since the software is compliant with FDA 21 CFR Part 11.