Which indicator class is a single-parameter indicator that responds to one critical process parameter such as time or pressure?

• A. Class II
• B. Class III
• C. Class I
• D. Class IV

Answer: (B)

A single-parameter indicator is designed to respond to one critical process parameter during sterilization. Class III indicators are built to confirm that a specific parameter—such as temperature, time, or pressure—has been reached in the cycle. They provide focused verification of that single requirement, rather than signaling exposure alone or overall process performance. By contrast, Class I indicators show that the item was exposed to the process, Class II indicators (like Bowie-Dick) assess broader cycle performance such as air removal and steam penetration, and Class IV indicators monitor two or more parameters simultaneously. So, for confirming one critical parameter was achieved, Class III is the best fit.