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Qualifying Your Autoclave

To ensure that your process continues to provide safe and sterile results, your autoclave must comply with established standards and norms (EN 285 and ISO 17665). In order to successfully do this, autoclaves require periodic qualification and validation to prove that they sterilize within their qualified parameters – and thereby provide completely clean and sterile materials and equipment.

The requirements for testing your autoclave depends on the country. In Europe, the standardized cycles are 121 °C for 15 minutes or 134 °C for 3 minutes.

In addition to achieving the appropriate temperatures and time periods, there are other critical measurements that you should consider:

  • Equilibration Time:
    The equilibration time is the time between your first sensor reaching the set temperature and your last sensor to do so – and serves to indicate the homogeneity of your autoclave
  • Spread of Temperatures:
    The spread of temperatures in your autoclave indicates the distribution of heat within the chamber during sterilization
  • Sensor Deviations:
    Indicates if your temperature sensors remain within their acceptable range


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IQ and OQ Qualifications

The qualification of an autoclave consists of an installation qualification (IQ) and operational qualification (OQ):

  • Installation Qualification:
    This verifies that your system was installed properly – and is typically performed by the system provider
  • Operational Qualification:
    This tests whether your system works as intended or not. To perform an OQ, you need high-end measuring equipment to accurately determine the functionality of your device

Once your autoclave has been proven to work properly, it must also prove that it sterilizes your materials properly too – which is where the validation process comes in.


Autoclave Qualification Medical

Validating Your Process

According to international regulations, your steam sterilization process must be validated at least once a year to ensure a sterile result. This requires accurate measuring equipment to gather data on temperature, pressure and time throughout the process.

The data you gather is then evaluated and compared to the relevant regulations in order to determine the quality of your sterilization – and thereby ensure compliance.


Ensuring Saturated Steam in Your Autoclave

Furthermore, it is critical that you are able to determine whether the steam used in your autoclave is saturated. Non-saturated steam places the entire sterilization process at risk, as the steam may not sufficiently reach every area of the equipment that’s meant to be sterilized.

To obtain saturated steam, use temperature mapping equipmentvalidated software, and potentially, an electronic Bowie Dick Test system. These systems will ensure that you comply with the required norms and prove that your steam is saturated – and thereby ready to sterilize.

IQ, OQ and PQ Qualifications

Unlike qualifications of your autoclave, where you only have to perform installation qualifications (IQ) and operational qualifications (OQ), the validation of your process also requires a performance qualification (PQ).

  • Installation Qualification:
    Verifies that the system is installed properly
  • Operational Qualification:
    Verifies that your system works as intended
  • Performance Qualification:
    Verifies the effectiveness of your sterilization process for a specific cycle or load. To perform a PQ, you need high-end measuring equipment to accurately determine your result

The results from your validation analysis are then used to control whether or not your autoclave complies with international standards, such as ISO 17665.


Steam Sterilization Qualification Medical

Controlling Steam Quality with a Bowie Dick Test

To ensure properly sterilized products, testing an autoclave’s steam penetration ability is crucial. This requires running a Bowie Dick test program.

The Bowie Dick test is an important daily routine control conducted on autoclaves. The purpose of which is to ensure proper penetration of steam, to allow it to successfully reach every corner of your chamber and product. Fully sterilizing it upon contact.


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A Bowie Dick test is, however, only as reliable as the piece of third-party equipment gathering the data. Which is why Ellab has developed SteriSense, the highly innovative and user-friendly electronic Bowie Dick test system, as the ideal solution.

Bowie Dick Test SteriSense

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Choosing the Right Equipment for Validation and Qualification

Both wireless data loggers and thermocouple systems are a suitable choice when looking for qualification and/or validation equipment for steam sterilization and autoclaves.

Wireless loggers are, due to the RTD sensor design, very accurate and stable, which makes them the ideal option for both qualifying the autoclave and validating the steam sterilization process.

A wired thermocouple system can also be used and may initially be the more economical option but will ultimately require far more resources to operate – resulting in challenges that could be avoided by using a wireless system. This is due to wireless data loggers being much easier to setup and control when compared to its cabled counterpart.

When using a wired thermocouple system for autoclave validation, there is the added challenge of maintaining the pressure and vacuum integrity. This is due to the necessity of using a feed-through system to allow the thermocouples into the chamber. Ellab’s feed-through system has been tested rigorously to ensure minimal leakage and optimal qualification efficiency.

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The Steam Sterilization Process

The steam sterilization principle is centered around exposing items to steam contact for a specified amount of time and under specified temperature conditions. Steam sterilization is typically used in hospitals for sterilizing the surfaces of wrapped goods or hollow items, and contains three important parameters: Temperature, steam under pressure and time.

The process is conducted by supplying dry, saturated steam under pressure into an autoclave. The heat from the condensation of steam envelops the items in the sterilizer and kills the microorganisms in an easy and fast manner. It does so by irreversibly damaging the cells by coagulation.

Steam sterilization takes a minimum of 15 minutes at 121 °C and a pressure of 2 ABS – or a minimum of 3 minutes at 134 °C and a pressure of 3 ABS for the items to be sterilized. However, cycle times may be longer depending on the particular items being sterilized. Objects that are sterilized with steam are often non heat-sensitive items, e.g. simple surgical instruments, dental instruments, reusable medical equipment, textiles or surgical equipment with cavities.

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Documenting the Process

For steam sterilization to be effective, the steam within your autoclave has to be saturated as this transfers far more energy from the steam to the product. To facilitate the validation of this parameter, the ValSuite software includes a saturated steam analysis that automatically correlates the temperature and pressure from within your autoclave.

To document the validation of the steam sterilization adequately, a diagram can be created that showcases all sensor ID’s in their exact position within your autoclave. This setup is easily performed in ValSuite Pro by integrating the session data with predefined schematics, pictures and Word documents.

ValSuite also allows you to easily generate and print various reports that can be kept on hand for audits and general documentation purposes.

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Ensuring Accuracy with Calibration

A typical, but critical, factor when validating steam sterilization is the calibration of temperature sensors. It is essential that operators can demonstrate that the sensors were within an acceptable accuracy range when they were used.

This means calibrating shortly before the validation run (Pre Calibration) and then checking the accuracy afterwards to ensure that they are still within the predefined tolerances (Post Calibration). Using the built-in calibration functionality in ValSuite, operators can calibrate Ellab sensors at regular intervals.

The software then generates an easy-to-read calibration report that includes all measurements and tolerances that were defined by operators. 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) to ensure that they function at optimal capacity.


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.

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How a Steam Sterilizer/Autoclave works

A steam sterilizer (or autoclave) is a high-pressure vessel with a sealed lid/door and gasket (the sterilizing chamber). The chamber is also equipped with an air removal system and a control system consisting of a timer, pressure control valve and safety valve. Autoclaves make use of pressurized steam at around 115-134 °C to heat the load and achieve sterilization.

Sterilizers come in many sizes, from small bench-top portable laboratory autoclaves to large production autoclaves. The larger autoclaves are usually built into the walls, from which “contaminated” products enter one side and the sterilized product exits on the other (inside a clean room).

They are typically used for sterilizing large volume of utensils and are rather advanced in design and control. They tend to be cylindrical, as this design has proven to be very strong when it comes to high and low amounts of pressure. Steam sterilizers are typically used for sterilizing products within the medical and pharmaceutical industries.

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ValSuite® Software Reports

Steam Sterilization

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Lethality F0
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Process Graph 1
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Process Graph 2
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Unit Report
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Validation Report
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