Chemical Indicators are important!

Chemical Indicators are important!

Chemical indicators (CI):

Class 5 integrating or Class-6 emulating indicators should be used for monitoring each sterilization load.

Let’s be more specific:

Up to Class 4, CI are called sterilization process indicators because they respond to at least one of the variables of time, temperature and pressure. They are inexpensive and are built into most of the sterilization packaging materials on the market including strips, tape, pouches and tubing. They are best used in conjunction with the other indicators mentioned below and third party biological testing services.

SciCan Statim Class 4 Sterilization Monitor and printout from Statim 5000

Class 5 are called integrating indicators (integrators) because they are designed to test all three variables.

Class 6 are called emulating indicators (emulators) because they are even more precise than Class 5 and designed to respond to a specific sterilization program. Class 6 (emulators) are proposed as an equivalent to biological indicators (spore testing) in terms of difficulty to falsify, and are being tested in long term studies to determine if it will be feasible to use them *instead* of biological indicators.

Class 6 (emulators) are most commonly used inside a sealed specialized container designed to challenge the autoclave’s air removal capability (helix test as shown below) and will fail with a common gravity displacement (type N) autoclave program. An autoclave such as the Statim or Bravo with dynamic air removal will effectively change the emulator CI inside the container through a meter of thin (2mm ID) tubing as per EN 13060.

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Question: Are Class 6 Chemical Indicators (CIs) better than Class 5 Chemical Integrators?

Answer: No. There are 6 classes of CIs that are classified by how each product is used to monitor the steam sterilization cycle (see table below).

It is important to keep in mind that these classifications are NOT ranked in order of importance or performance.

Class 1: Process IndicatorsFor use on the exterior of individual packs, peel pouches, containers, etc… to indicate exposure to the sterilization process

Class 2: Indicators for Specific Tests
For use in specific test procedures (i.e. Bowie-Dick Type Test)
Class 4: Multi-Variable IndicatorsFor use inside individual packs, peel pouches, containers, etc… Reacts to two or more of the critical variables of the sterilization process
Class 5: Integrating IndicatorsFor use inside individual packs, peel pouches, containers, etc… Reacts to all critical variables of the sterilization process and the Stated Values must be equivalent to or exceed BI performance requirements
Class 6: Emulating IndicatorsFor use inside individual packs, peel pouches, containers, etc… Reacts to all critical variables of the sterilization process for a specified sterilization cycle

Question:  What are the differences between Class 5 and Class 6 CIs? 

Answer:   Class 5 Chemical Integrators react to the three critical variables of a steam sterilization cycle (time, temperature, and the presence of steam). In addition, their performance is required to correlate to a biological indicator (BI). As a result, Class 5 integrator results are similar to those of a BI and can detect failures where the selected temperature isn’t reached. This failure condition is likely to occur when there is incorrect packaging and loading, air/steam mixtures, and/or incorrect cycle for load contents.

In contrast, Class 6 CIs react to the three critical variables for a specified cycle, and their performance may or may not correlate to a BI. Class 6 CIs are sometimes referred to as cycle specific indicators. It is important to realize that if you run multiple exposure times and temperatures, you must use a distinct Class 6 CI to monitor each cycle time and temperature. And because Class 6 CIs are not required to correlate to a BI, a Class 6 indicator could reveal a pass where a BI would indicate a failure.

1 thought on “Chemical Indicators are important!”

  1. 1. At least one Class 5 integrating or Class-6 emulating indicator should be used for monitoring each sterilization load.
    2. At least one Class 4 or lower chemical indicator should be included with each wrapped item sterilized in each load.

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