- Class 5 integrating indicators used for pack control as a method for monitoring sterilization process conditions inside each pack
- Can also be used inside a process challenge device (PCD) to release processed items, excluding implants (load control), however they do not replace the use of biological indicators
- Consist of a paper wick and steam and temperature sensitive chemical contained in a paper/film and foil laminate envelope
- The migration is visible through a window marked unsafe or safe
