Autoclave Validation / Qualification is mandatory for all machines used for biological sterilization, in the biomedical and pharmaceutical industries. Sterilization can be accomplished by either physical or chemical means. The principal physical means is autoclaving; other physical methods include boiling and dry heat.

Chemicals used for sterilization include the gases ethylene oxide and formaldehyde, and liquids such asglutaraldehyde . Of all these sterilants, autoclaving is the fastest and most reliable, which is why the regulators always scrutinize autoclave validation / Qualification activities.

Here are 10 items to consider when qualifying autoclaves.

1. Testing of Steam for Porous Product Sterilization

Before commencing temperature testing the correct conditions must be satisfied. The first condition for sterilization of porous product is saturated steam quality. The ideal for steam sterilization is dry saturated steam and entrained water (dryness fraction ≥ 97%). The largest heat transfer occurs when the steam is at boundary conditions. If the steam is dry or contains gas then it cannot condense and its effectiveness is reduced.

2. Equipment Used for Testing

The equipment used must support 21 CFR Part 11 and must be of adequate accuracy. Testing with equipment that is not appropriate can be a major problem so also buy from a trusted vendor. As a small temperature range is required for accuracy (A few degrees) the accuracy of the equipment is very important for the overall measuring chain.

3. System Description of Autoclave

The first impression is very important when the qualification of critical equipment such as an autoclave is at stake. A good description of the system in a protocol shows that you understand how the process works and which critical points you need to keep under control. This description must contain the programs that are used, how they work, how many, where the control probes are located and what regulates this process.

4. Operating Instructions, Calibration and Maintenance

Before the temperature is tested it must be checked whether the operating instruction are valid, whether the instruments are calibrated and what was changed in the system since the last qualification occurred.

Operating Instructions must include parameters of sterilization, the scheme item and position of the control probes in the chamber. The emphasis is on the calibration of instruments because small errors in temperature can affect the Fo value to a great extent.

5. Procedure

One of the most common mistakes is inaccurate testing procedures. The test procedure must be unambiguous and accurate and must not leave the possibility for different interpretations.

Ambiguous: Put the thermocouple in a glass bottle.

Unambiguous: Put the thermocouple in a glass bottle at the contact between the bottom of the bottle and the side of the bottle (This is the most critical place to collect condensate).

6. Load

The most common objections are about loads. That they are not sufficiently described and that regular production does not reflect the qualified load being used.

This can be avoided by item photographing and releasing the same patterns in the protocol and work instructions. This will avoid the arbitrary interpretation of descriptive configuration.

Although sometimes this may seem trite the differences in the temperature profiles of the solution and air filters can be great. Pay special attention to the worst case loads and explain the rationale (mostly filter and silicone hose).

7. The Position of the Thermocouples

The position of the thermocouples must be unambiguous and precise to avoid different interpretations by individuals that perform tests or inspections. You do not want to enter into a debate about where the thermocouple is positioned.

Of course, the critical areas must be covered, and this must be explained in the rationale. When sterilizing liquid loads studies must be done to define coldest and warmest point for min and max load.

8. Acceptance Criteria in the Heat Penetration Tests

Since there are differences in the standards (e.g. PDA Technical Report and EN 285) it would be best if all eligibility criteria are taken into account. Special emphasis should be on equilibration time and temperature because it is a requirement for a good Fo.

9. Deviations

Deviations cannot be forgotten as they may be encountered regularly throughout the qualification process. A robust deviation management process should exist as they may impact the quality of the product. Good handling of deviations help us to improve our qualification, though they are often viewed negatively and not as a mechanism for process improvement.

10. Reports

The report should be accurate as it eliminates the use of data from the protocol and the ability to find errors in them. The report should contain the time and the date of tests, parameters, results related to temperature, BI results , positions of thermocouples, Fo and comparison of results from initial and previous qualification in order to see in which direction the process is moving.