The chemical indicators or indicator systems described in this part of ISO 11140 The six indicator types described in the main body of this part of ISO 11140 are categorized according to their performance requirements. The chemical indicators within each of these categorizations are further subdivided by the sterilization process for which they are designed to be used. These categorizations have no hierarchical significance. Attainment of the chemical indicator’s end point should not be regarded as an indication of attainment of an acceptable sterility assurance level, but rather one of many factors which should be taken into consideration when judging the acceptability of a sterilization process.
What Are the 6 Types of Chemical Indicators for Steam Sterilization?
Sterilization practices are essential for patient safety because medical instruments must be processed under validated conditions before use. Chemical indicators for sterilization help users check whether key sterilization parameters, such as exposure to steam, time and temperature, have been reached during the cycle.
ISO 11140-1 classifies chemical indicators into six types according to their intended use and performance characteristics. Although the terms “class” and “type” are often used interchangeably in the market, “Type 1” to “Type 6” is the preferred wording when referring to ISO 11140-1.
Type 1 Process Indicators
Type 1 chemical indicators are process indicators. They are designed to show that an item has been exposed to a sterilization process. They are commonly used on sterilization packaging, tapes, labels and pouches to distinguish processed items from unprocessed items.
Type 2 Indicators for Specific Tests
Type 2 indicators are used in specific test procedures. Examples include Bowie Dick test packs and Helix test systems for checking air removal and steam penetration in pre-vacuum steam sterilizers.
Type 3 Single-Variable Indicators
Type 3 indicators respond to one critical variable of the sterilization process, such as temperature. They are less commonly used than multi-variable or integrating indicators.
Type 4 Multi-Variable Indicators
Type 4 indicators respond to two or more critical variables of a sterilization process. They are often used as internal chemical indicators inside packs, trays or pouches to provide evidence that sterilizing conditions have reached the indicator location.
Type 5 Integrating Indicators
Type 5 integrating indicators are designed to respond to all critical variables of a specified sterilization process. For steam sterilization, they provide a high level of process monitoring and are commonly used for routine load monitoring and pack monitoring.
Type 6 Emulating Indicators
Type 6 emulating indicators are cycle-specific chemical indicators. They are designed to respond to all critical variables of a specified sterilization cycle, such as 134°C for 3.5 minutes. Type 6 indicators are chemical indicators, not biological indicators.
In conclusion, chemical indicators for sterilization are divided into six ISO 11140-1 types, each with a specific monitoring purpose. Selecting the correct type helps healthcare facilities monitor sterilization processes, detect potential failures and support infection control procedures.
Additional Resources
- FDA Guidance on Sterilization
- ISO Standards for Sterilization: ISO 11607 and ISO 11140
- Ethylene Oxide Sterilization: Principles and Practices
