The 3M recommended best practice is to use a Class 5 chemical indicator in every pack.
The indicator should be placed inside each package in the areas that are most difficult for the sterilant to penetrate. For a wrapped fabric pack this is usually the geometric center, but for complex instruments you should check with the manufacturer. They will know from their testing where those areas are. For unwrapped loads, at least one indicator should be placed in the tray with the items to be sterilized.
The chemical indicator is retrieved at the time of use and is interpreted by the user. If the result of the chemical indicator suggests inadequate steam processing, the contents of the pack should not be used. In addition, all of the items from that pack should be returned for reprocessing, and the appropriate supervisor should be notified. A decision should be made, based on the results of other monitoring tools such as physical monitors, indicators elsewhere in the load, and biological indicator results, if available, whether or not the entire load should be recalled.
For detailed information on pack control procedures and product usage, please refer to the following documents (requires Adobe® Reader® or Adobe® Acrobat®):
Chemical Indicators - It's Not Just a Numbers Game, HealthVIE © January 2011 (PDF, 612 KB)
Pack Control Product Information