Steam Sterilizer Validation
The most common sterilizing agent in an autoclave is steam. However, some autoclaves use different methods such as water cascade, water spray or a steam-air mixture.
The latent heat released when steam condenses on the items to be sterilized makes this process very efficient. Sterilization temperatures range from 115 to 134°C. Common sterilized products and containers are:
- Pouch/IV bag
- Medical equipment
An autoclave is a vessel that uses pressurized steam to heat the product to achieve sterilization. Autoclaves come in a wide variety of sizes, from small bench-top laboratory autoclaves to large production autoclaves. Larger autoclaves can be used for sterilizing high volume parenterals such as those found in pouches. Bottles and ampoules are typically sterilized in smaller autoclaves. Whatever the nature of the load, the product is loaded on trays or in cages to optimize the distribution of the load.
For validation purposes it is important that the load is standardized, therefore full loads are usually used.
Autoclaves can be used for sterilization of liquids in various containers such as bottles, vials, ampoules, bags and medical equipment.
In most cases it is necessary to monitor the temperature of the product and the pressure of the autoclave during sterilization. This could be during batch production, cycle development and validation.
For this reason, Ellab offers a wide range of fixtures and fittings.
The reproducibility, which is enabled by the fixtures and fittings, makes re-validation much easier and reliable.
The requirements for testing or validating autoclaves depend on the type of use and the country. Commonly used standards and guidelines are ISO EN 285, ISO EN 17665, ISO EN 11138, HTM 2010 and PDA Technical Report No. 1 Validation of Moist Heat Sterilization Processes.
Guidelines state that 11 temperature-measuring points are needed when performing a heat distribution study of an autoclave that is from 1.5 to 2.5 m3.
This number is reached by placing one sensor in each of the eight corners in the autoclave, one in the center, one close to the drain and one next to the autoclave’s temperature sensor.
In addition to achieving minimum and maximum temperatures for set time periods, there are a number of other measurements which many users find critical. These include the equilibration time, which is the difference between the first sensor achieving sterilization temperature and the last. Also, the spread of temperatures during the sterilization period and the deviation between individual temperature sensors over the sterilization period are considered critical during the validation of autoclaves.
Another critical parameter is the use of saturated steam. For sterilization to be effective the steam has to be saturated as this transfers most energy from the steam to the product. To facilitate the validation of this parameter the ValSuite™ Pro software includes saturated steam analysis that correlates temperature and pressure automatically.
To document the validation adequately a diagram must be made that shows all the sensors´ ID numbers related to their exact position in the autoclave. This is easily done in ValSuite™ Pro by integrating the data session with predefined schematics, pictures and Word documents.
A critical factor when validating autoclaves is the calibration of temperature sensors. It is essential that the user can demonstrate that the sensors were within an acceptable accuracy when they were used. This means calibrating shortly before the validation run (referred to as Pre Calibration) and then checking the accuracy afterwards to ensure that they are still within predefined tolerances (referred to as Post Calibration). Using the built-in calibration functionality, users can calibrate the Ellab sensors at regular intervals. The ValSuite™ Pro software generates an easy to read calibration report that includes all measurements and tolerances that are defined by the user. It is recommended that Ellab sensors and probes are sent in at least once a year for factory calibration (which includes a traceable calibration certificate).
Ellab Validation Solutions
Both the E-Val™ Pro thermocouple system and the TrackSense® Pro wireless data loggers are well suited for the validation of autoclaves. For validating the sterilization process according to the predefined acceptance criteria, the ValSuite™ Pro software is a valuable tool.