Ask the Editors
What is the difference between the various types of chemical indicators for heat sterilization?
Chemical indicators use sensitive chemicals to assess physical conditions (e.g. time and temperature) during the sterilization process. Common forms of these indicators include paper strips, labels, and steam pattern cards. Because chemical indicators do not contain bacterial spores, they do not prove that sterilization has been achieved. They do, however, allow detection of certain equipment malfunctions and can help identify procedural errors.
External indicators applied to the outside of the package can verify that the package has been exposed to the sterilization process. However, some external indicators change color long before appropriate sterilization conditions have even been reached. Autoclave tape is an example of this kind of indicator. External indicators are primarily used to identify packages that have been processed through a heat sterilizers, thus preventing the accidental use of unprocessed items.
Recommendations include the use of an internal chemical indicator inside each package to evaluate whether the instruments were exposed to the sterilization conditions. In other words, internal chemical indicators are used to ensure that the sterilizing agent has penetrated the packaging material and actually reached the instruments.