Steam Sterilization

Manufacturers of Reusable Medical Devices designed to be sterilized by steam must provide detailed instructions for reprocessing. The manufacturer shall validate that the instructions provided are capable of sterilizing the medical device for its intended use. The validated packaging configuration as well as steam sterilization parameters must be provided to the health care facilities in these instructions.

The most common steam sterilization cycles used in the industry are the gravity-displacement and dynamic-air-removal. In gravity-displacement the steam enters the sterilizer chamber and displaces the residual air through an open vent. A more efficient cycle type is the dynamic-air-removal, specifically the prevacuum cycle, in which the air is removed from the chamber and load by means of pressure and vacuum excursions. Flash sterilization cycles consist of higher temperatures for a shorter time and are designed for processing patient care items for immediate use. At Pacific BioLabs the overkill sterilization model is used with these two cycle types to demonstrate a 10-6 Sterlity Assurance Level (SAL) when performing a steam sterilization validation. For more information see ANSI/AAMI ST79:2006 Comprehensive guide to steam sterilization and sterility assurance in health care facilities.

The following are the most common steam sterilization cycles validated at PBL:

Cycle TypePackagingTemp (°C/°F)Minimum Exposure Time (minutes)
Gravity-DisplacementWrapped Instruments121/25030 minutes
Gravity-DisplacementWrapped Instruments132/27015 minutes
Gravity-DisplacementWrapped Instruments135/27510 minutes
Gravity-Displacement FlashUnwrapped Non-Porous Instruments132/2703 minutes
Gravity-Displacement FlashUnwrapped Non-Porous Instruments135/2753 minutes
Prevacuum FlashWrapped Instruments132/2704 minutes
Prevacuum FlashWrapped Instruments135/2753 minutes
Prevacuum FlashUnwrapped Non-Porous Instruments132/2703 minutes
Prevacuum FlashUnwrapped Non-Porous Instruments135/2753 minutes

Additionally, the following table lists minimum cycle times for gravity-displacement steam sterilization cycles:

ItemExposure Time at 121°CExposure Time at 132°CExposure Time at 135°CDrying Times
Wrapped instruments
30 minutes
15 minutes
15-30 minutes
10 minutes
30 minutes
Textile packs
30 minutes
25 minutes
15 minutes
10 minutes
30 minutes
Wrapped utensils
30 minutes
15 minutes
15-30 minutes
10 minutes
30 minutes
Unwrapped nonporous items (instruments)
3 minutes
3 minutes
0-1 minute
Unwrapped nonporous and porous items in mixed load
10 minutes
10 minutes
0-1 minute

For dynamic-air-removal steam sterilization cycles, the following table lists minimum cycle times:

ItemExposure Time at 132°CExposure Time at 135°CDrying Times
Wrapped instruments
4 minutes
20 to 30 minutes
3 minutes
16 minutes
Textile packs
4 minutes
5 to 20 minutes
3 minutes
3 minutes
Wrapped utensils
4 minutes
20 minutes
3 minutes
16 minutes
Unwrapped nonporous items (instruments)
3 minutes
3 minutes
NA
Unwrapped nonporous and porous items in mixed load
4 minutes
3 minutes
NA

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