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Getting to the Bottom of Sterilization Classes

All American Electric Autoclave SterilizerIn our new Sterilization Series, we discussed sterilization methods overall, sterilization by heat, and then, more specifically, sterilization by steam, which is the sterilization method used most effectively in tattoo and piercing shops via autoclaves. When you use an autoclave to sterilize tattoo and piercing tools and body jewelry in your shop, it's important to also utilize indicators that show whether or not each sterilization cycle was effective. These chemical indicators (CIs) test elements of the sterilization process itself, and some also test for biological indicators that a sterilization process was successful.

CIs are divided into several classes that provide varying degrees of information about how well your autoclave is working. To understand the value of these classes, you have to first know the difference between process and biological indicators.


Sterilization Process Indicators vs. Biological Indicators

A process indicator's purpose is to confirm that a set of packaged items underwent a sterilization process. All of our Precision sterilization pouches have basic process indicators built into them, as shown in the sterilization pouch image below. When one of these packages has been through an autoclave's steam sterilization cycle, the process indicator turns from blue to black. If you were to sterilize the same pouch via a chemical process utilizing EO gas, the process indicator would turn from pink to brown.

Sterilization Pouches Have Process Indicators Built Into Them

The only downside to this basic type of built-in process indicator is that it's external, which means that technically you could hold it over a steaming tea kettle, change the indicator from blue to black, and say the item inside the pouch had been sterilized. That's why we also include internal process indicators in our Precision sterilization pouches. Internal process indicators that are placed inside sterilization pouches before they're sealed are even more useful than package process indicators, because they will only change color if the entire package was placed inside an autoclave and run through a steam sterilization cycle. It's something you can show your clients as extra proof that you didn't cut corners and that you actually ran the items you're using in their modification through an autoclave.Propper's Vapor Line Steam Sterilization Biological Indicators With our Precision autoclave pouches, you would just peel off the included internal process indicator and place it inside the bag before sealing and autoclaving it. That way you have twice as much proof that you properly sterilized tools you're using in a body modification.

Process indicators are useful, because they confirm that an item underwent a sterilization process and that, depending on the test, specific elements critical to the success of that sterilization process did in fact occur. The addition of a biological indicator (BI) makes a chemical indicator test even more thorough. BIs check for spores as added assurance that an item was fully sterilized.

Propper’s Vapor Line® Steam Sterilization Integrators (shown to the left) are a great example of these super-thorough sterilization tests that combine process indicators and biological indicators. They monitor saturated steam, temperature, and the time an autoclave operated within that temperature range--three things that must be in balance for an autoclave to work effectively. They also check to make sure no spores remain at the end of the test. Propper's tests and other CIs like them prove with relative certainty that an item was actually sterilized to the necessary degree, obliterating all microorganisms that may have been clinging to it before being sterilized.


Sterilization Classes

Chemical indicators (CIs) are divided into several classes that react to some component of the sterilization process. Classes 1-4 are simply sterilization process indicators that tell varying degrees of information about whether or not a sterilization process occurred. They range from indicating only that an item was sterilized by steam to indicating that specific elements that are critical to a successful sterilization process actually occurred. CIs belonging to classes 5 and 6 are the most thorough sterilization tests, as explained below.

  • Class 1 includes process indicators like those built into sterilization pouches and the internal steam indicators detailed above.
  • Class 2 includes those chemical indicators used for specific tests. For instance, a Bowie-Dick Test checks for air leaks and proper air removal from a sterilization device.
  • Class 3 indicators are single-variable indicators. In an autoclave, steam, temperature, and time must be in perfect balance for the contents to be completely sterilized. A class 3 indicator would test to ensure that one of these critical elements was working properly at the time an item was autoclaved.
  • Class 4 indicators are multi-variable biological indicators that test to ensure that two or more critical elements were working properly at the time an item was autoclaved.
  • Class 5 indicators are called integrating indicators. They're designed to test all components that are critical to the sterilization process and must include a biological indicator of the test's effectiveness. These are the most accurate of the internal CIs. The Propper’s Vapor Line® Steam Sterilization Integrators shown above are Class 5 integrating CIs.
  • Class 6 indicators are called emulating indicators. Unlike Class 5 CIs, they're not required to correlate to a biological indicator. They test that all 3 critical elements worked within an autoclave cycle, but without a biological indicator, Class 6 CIs may actually be inferior to Class 5 CIs.Autoclave Indicator Tape

For your clients' safety, it's ideal to place a Class 5 CI in each pouch you run through your shop's autoclave. Alternatively, some shops choose to use Class 1 - 4 CIs ranging from built-in indicators to autoclave indicator tape to internal steam indicators with each batch of tools or jewelry sterilized and then run a spore test through their autoclave at least monthly. Whichever method you choose, the important thing is that you're regularly checking to ensure your autoclave is working properly for your clients' protection.

To learn more about chemical indicators, biological indicators and the 6 sterilization classes, read our Sterilization Classes article.