Chemical indicators are medical devices for monitoring a sterilization process. The device is designed to respond with a characteristic chemical or physical change to one or more of the physical conditions within the sterilizing chamber. Chemical indicators are intended to detect potential sterilization failures that could result from incorrect packaging, incorrect loading of the sterilizer, or malfunctions of the sterilizer. The “pass” response of a chemical indicator does not prove the item accompanied by the indicator is necessarily sterile. The Association for the Advancement of Medical Instrumentation has defined five classes of chemical indicators.
- Class 1 chemical indicator: A process indicator often referred to as an external indicator. They distinguish between processed or unprocessed items and indicate that they were exposed the sterilizer. These are seen as indicators on pouches, sterilizer tapes or labels.
- Class 2 chemical indicator: Is designed for a specific test procedure (e.g. The Bowie-Dick test used to determine if air removal has been adequate in dynamic-air-removal sterilizers)
- Class 3 chemical indicator: Is a single parameter indicator. It is designed to react to one of the critical parameters of sterilization.
- Class 4 chemical indicator: Is a multi-parameter indicator. It is designed to react to two or more of the critical parameters of sterilization.
- Class 5 chemical indicator: Is an integrating indicator. This chemical indicator reacts to all three parameters of sterilization which include proper amount of time, temperature and pressure of the sterilizer. They have been correlated to the performance of a biological indicator when used according to the manufacturers conditions noted on the label.