Cycle Development

Cycle development is performed to provide you with a sterilization process and recipe that works for your load.  This process will result in parameters (i.e. cycle type, temperature, time, etc.) that can be validated. Ideally, cycle development should begin before the sterilizer is purchased, since the cycle types will affect the type of autoclave you need, and changes in the field after installation are generally difficult and expensive. At the very least, cycles should be developed prior to performing a full validation of the autoclave and, more specifically, before Performance Qualification (PQ) validation.

It’s worth pointing out that in most laboratories cycle development isn’t required or has already been performed by others in the lab. Cycle development is most commonly used for biotechnology, pharmaceutical, or medical device companies that are regularly validat­ing their autoclaves and/or sterilizing new or unique loads.


  1. Determine cycle type:  gravity, prevac, liquids, etc.
  2. Once the cycle type is determined you must decide on the key cycle parameters: sterilization temperature and sterilizer time. The vast majority of loads sterilized in the laboratory setting are sterilized at 121.1°C/250°F for 30-90 minutes. For loads that are sensitive to heat, contact your autoclave validation expert for advice on calculating your sterilization time using the F0 relationship.
  3. Once you have determined your cycle type and parameters, you must validate the cycle to ensure the load will be sterile. These test cycles should be loaded in a way that is representative of the actual load to be sterilized. It is recommended to run your test cycles at half of the desired steriliza­tion time (this is referred to as the “half-cycle” method).  Sterility testing is confirmed with the use of biological indicators (BIs). The most common test organism for steam sterilization is Geobacillus stearothermophilus. BIs are placed in intimate contact with the load and are placed throughout the chamber. Typically, at least 10 BIs are used per cycle. If all BIs show no growth (i.e. all the bacteria are destroyed) in three successive cycles, you have validated the cycle.
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