6 ISO Types of Chemical Indicators for Steam Sterilization
Key Takeaways:
- Chemical indicators verify sterilization conditions in autoclaves and steam sterilizers.
- ISO 11140-1:2014 defines six types of CIs, each with specific uses and performance traits.
- Type 1 confirms exposure; Type 2 (Bowie-Dick) tests air removal efficiency.
- Types 3–6 increase specificity, with Type 5 and Type 6 tracking all key parameters.
- Choose the right indicator based on process, monitoring needs and regulations.
Chemical indicators for autoclaves and steam sterilizers play a critical role in sterility assurance programs. There are many types of chemical indicators, such as bowie dick test packs and chemical indicator strips.
All chemical indicators are designed to respond to physical conditions inside the sterilizing chamber. This validates that an autoclave or steam sterilizer is working properly. It also verifies that it met the conditions for sterilization to occur.
Standards for Chemical Indicators
The International Organization for Standardization (ISO) issues many standards for sterilization processes. Chemical indicators must adhere to these manufacturing and application standards, and guidance documents.
ISO 11140-1:2014 is identical to:
- BS EN ISO 11140-1:2009
- ANSI/AAMI/ISO 11140-1:2014
ISO 11140-1:2014 replaces previous standards:
- EN867-1
- ANSI/AAMI ST60:1996
The most current standard is ISO 11140-1:2014. It defines 6 different types of chemical indicators for sterilization.
6 ISO Types of Chemical Indicators for Steam Sterilization
ISO 11140-1:2014 classifies chemical indicators for autoclaves and sterilizers as follows:
- Type 1: Process Indicators
- Type 2: Specific-Use Indicators
- Type 3: Single-Variable Indicators
- Type 4: Multi-Variable indicators
- Type 5: Integrating Indicators (Integrators)
- Type 6: Emulating Indicators (Cycle Verification Indicators)
The types are not ranked by level of importance. Type 1 is not better than type 6. Each type simply denotes performance characteristics and intended use of chemical indicators.
ISO 11140-1:2014 section 4.1
"The classification structure used is solely to denote the characteristics and intended use of each type of indicator when used as defined by the manufacturer. This classification has no hierarchical significance."
Since performance requirements are distinct, chemical indicators should only comply with one type. This chart summarizes the different ISO types of chemical indicators. It also provides examples of applications and STERIS Life Sciences products available for each type. Use it to help choose the correct chemical indicator for monitoring specific sterilization processes.
6 ISO Types of Chemical Indicators for Steam Sterilization
Types
Type 1: Process
What They Indicate
One or more critical variables in the sterilization process
The unit has been directly exposed to the sterilization process
Application Example
Autoclave tape or chemical indicator strips
Located inside or attached to the outside of packs
Provide visual confirmation of exposure to sterilization process
STERIS Life Sciences Products
VERIFY™ Valueline Class 1 Steam Chemical Indicator (PCC009)
Steam Indicator Tape (260010)
Types
Type 2: Specific-Use
What They Indicate
Defined in relevant sterilization standards for specific test procedure
Application Example
Bowie-Dick test packs
Test air removal in a prevacuum steam sterilization cycle
STERIS Life Sciences Products
Steraffirm® Bowie-Dick Test Pack (EQC003)
VERIFY™ Bowie-Dick Test Packs (EQC009, EQC010)
Daily Air Removal Test–DART® (NB113, NB215)
VERIFY™ Bowie-Dick Test Card (S3095)
See Full Table
Types
Type 3: Single-variable
What They Indicate
One critical variable in the sterilization process
Exposure to a sterilization process at a stated value (SV) of the variable
Application Example
Chemical pellet
Melts at a specified temperature
Demonstrates the steam sterilization process has achieved a specified temperature
STERIS Life Sciences Products
Not currently available
Types
Type 4: Multi-variable
What They Indicate
Two or more critical variables in the sterilization process
Exposure to a sterilization cycle at stated values (SVs) of the variables
Application Example
Chemical indicator tubes
Change color only when exposed to a given temperature for a specified time in a steam sterilization application
STERIS Life Sciences Products
Steraffirm™ Sterilizer Control Tube, Steam at 121°C/250°F for 15 minutes (PCC024), or 12 minutes (PCC025)
Types
Type 5: Integrating (Integrators)
What They Indicate
All critical variables in the sterilization process
Stated values (SVs) meet or exceed performance requirements in the ISO 11138 series for biological indicators
Application Example
Moving front indicators
Respond to all critical process parameters
STERIS Life Sciences Products
VERIFY™ Steam Integrating Indicator (PCC065B, PCC065, PCC064)
Types
Type 6: Emulating (Cycle Verification)
What They Indicate
All critical variables for specified sterilization cycles
Stated values (SVs) are generated from the critical variables of the specified sterilization process
Application Example
Cycle-specific indicators
Typically placed in the pack, pouch or container
Respond to all critical process parameters for a specified sterilization cycle
STERIS Life Sciences Products
Steraffirm™ Steam Class 6 Emulating Indicators, Steam for 121°C/ 250°F for 15 minutes (PCC012)
Suggested Content
Mitigating Risk with Autoclave Air Removal Tests
Checklist: Positive Biological Indicator in Steam Sterilization
Steam Sterilization: The Importance of Air Removal and Verification
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