A Steam Class 5 indicator is an integrating chemical indicator used in steam sterilization (autoclaving) to check whether the required conditions for effective sterilization have been achieved. It is designed according to ISO 11140-1 standards and is considered one of the most reliable chemical indicators.
It works by using a special chemical substance or ink that changes color only when all the critical parameters of sterilization—temperature, time, and the presence of saturated steam—are met together. Because it responds to all these variables collectively, it is called an integrating indicator.
Class 5 indicators are placed inside instrument packs or trays during the sterilization process. This helps ensure that steam has properly penetrated to the innermost part of the load. The color change provides a clear and quick visual confirmation that the sterilization cycle was effective.
These indicators are highly accurate and their performance is close to biological indicators, making them more reliable than lower classes of chemical indicators. However, they do not directly confirm the destruction of microorganisms, so they are often used along with biological indicators for complete sterilization assurance.