An increasing number of applications in the chemical industry involve measuring nonconforming items, particularly in high‐purity processes or high‐yield processes. Dedicated monitoring tools such as the time‐between‐events (TBE) control charts have been developed for both discrete time (CCC‐charts) and continuous time (tr‐charts) for detecting any shifts in the process defect rate. However, most common performance metrics used in literature are not always appropriate and may not suffice to describe the efficiency of a monitoring system. The definition of conditional performance measures described in the literature is extended to TBE charts. These metrics are computed for Shewhart‐type TBE charts with run rules and used to compare these charts at different aggregation levels.