Alert LevelsAlert Levels should be

Alert LevelsAlert Levels should be set at levels that are near the top edge of normal data trends. Alert levels may be based on analysis and trending of historic performance data and are usually set at two standard deviations (2σ) from normal operating levels.An occasional Alert Level excursion that is barely above the Alert Level could be considered a normal expectation, as it is within the upper reaches of the normal operating trends for the system. Though such a level could be an early indication of a growing control problem, it could also be simply the variability of normal operating data. Responses to Alert Level excursions should include notification of appropriate quality, manufacturing, and maintenance personnel, along with closer attention being paid to the routine data. Frequent excursions beyond the Alert Level should not be expected and might also be considered out of trend.When data begins to drift outside of the normal trends and expected performance, notification of those who may potentially be affected, as well as resampling, may be appropriate to verify if the data trends are consistently higher (a possible developing control problem) or not (a possible sampling inconsistency or normal data variability).Where Alert Level excursions occur concurrently at multiple locations or sequentially at the same location, this may be an indication of a need for investigation and remediation and may be escalated to an Action Level excursion.