Autoclave temperature mapping qualification considerations
Steam Sterilization is common in the Life Sciences industry and is generally executed in autoclaves. Steam under pressure is used to kill microorganisms; the required time and pressure will vary based on the items being sterilized and the type of autoclave used. Common autoclave cycles include gravity, pre-vacuum and/or post vacuum, liquids and immediate use/flash. Below are common challenges, important considerations and Ellab’s solutions for autoclave temperature mapping qualifications.
Autoclaves present specific challenges when executing temperature mapping. Determining heat distribution and lethality begins with safely accessing the unit and placing multiple temperature sensors within the sterilizing chamber. The number of sensors and their positions are often dictated by norms or directives such as EN 285 and EN 17665 used in Europe.
Qualifying an autoclave with a thermocouple unit, such as Ellab’s E-Val Pro, requires a feed through system to pass the thermocouples into the autoclave while maintaining pressure and vacuum integrity. At Ellab we in-house manufacture our own feed through and have conducted robust testing verifying its efficacy against leaks.
Qualifying an autoclave with data loggers, such as Ellab’s TrackSense Pro series, eliminates the requirement of a feed through system and guarantees the test equipment utilized does not affect the pressure/vacuum integrity of the unit under test.
Prior to beginning an operational qualification (OQ); Cycle parameters should be established based on cycle development studies including a formal data analysis . The next step in a standard autoclave OQ is determining the worst-case location. This is defined as the most difficult area to bring up to exposure temperature. This testing is performed via an empty chamber temperature mapping. Based on individual cycle parameters, its entirely possible to have unique worst-case locations for each cycle. Due to this fact, it’s critical that each cycle is run and its worst-case location determined.
Loaded Chamber Performance Qualification (PQ) mapping can be significantly more complex. In general, PQ is where chamber load patterns are determined and the hardest to heat items in each load are identified.
There are two common methods for mapping load items during PQ:
- A fixed load approach is relatively straightforward. This type of validation is performed with a pre-determined set of items are placed in pre-chosen locations. This type of testing is easy to repeat because the same item goes in the same place for every load. It is limiting in the operating environment though, due to that fact that any load other than the exact load that was validated will result in a non-conformance.
- A variable load approach can be more challenging during qualification, it is accomplished by pre-determining a bracketed range of items and sizes of those items that constitute a maximum load for the autoclave. During cycle development, load mapping studies are used to determine the hardest item to heat, then preparing a worst-case load and placing the item in the worst-case location as determined during OQ. While this type of validation is more difficult and time consuming, this method lowers the risk of non-conformance in the operating environment due to the flexibility it allows operators when loading the unit.
Validated autoclaves require periodic re-validation. This is typically performed on a 6 or 12-month cycle or when crucial components are required or exchanged.
Solutions from Ellab
Ellab manufactures temperature mapping equipment specifically designed to function in autoclave environments including both thermocouple and wireless data logger systems. Specific sensors used in the mapping of autoclaves include temperature and pressure sensors. Ellab’s equipment is capable of determining the predefined maximum standard deviation of the validation sensors, and the allowed deviation from the mean value for each single validation sensors is not exceeded. Our equipment is available for purchase and/or rental.
Another option is that Ellab can provide on-site support with our highly trained engineers.
Ellab’s on-site services can assist in a variety of ways from protocol development, factory acceptance test (FAT), site acceptance test (SAT), cycle development, installation qualification, operational qualification, performance qualifications, and report generation.
- Highly trained staff. Efficient and knowledgeable about specific applications, industry expectations, and qualification methodologies.
- Quality of documentation practices and fast report turnaround times
- Equipment specifically designed for autoclave applications to handle repeated exposures to high temperature and pressure cycles
- Software designed to meet industry reporting requirements including validated Lethality (F0) calculations and EN285 & EN17665 pass/fail reports
Life science companies need to ensure they are qualifying their autoclaves based on the level of patient risk and that they are following the requirements of all applicable guidelines. This may include GLP, GMP, FDA, EU, or client specific requirements.