Management of change (MOC) is the process used to review all proposed changes to equipment, procedures, materials, personnel, and process operations before they are implemented to determine their effects on safety vulnerabilities. For example, standard operating procedures generally describe the acceptable operating ranges of process parameters (e.g., flow rates, concentrations, pH ranges, temperatures, pressures). A knowledgeable person should evaluate any proposed parameter changes to ensure safe operation. Operators should be made aware of changes and trained to respond with the appropriate actions if a parameter falls outside its acceptable range (e.g., notify supervisors, change process settings, shut down process).

Management of change is usually interpreted as relating to permanent changes, but temporary changes (e.g., abnormal situations, deviations from standard operating conditions, untrained personnel filling in during an expected absence) have been contributing factors in many catastrophic events over the years and should be managed as if they were permanent changes. Sometimes changes occur that are unplanned, but they should still be systematically managed and controlled to avoid problems. It is critical that an unexpected change be recognized by alert operators and resulting safety vulnerabilities be communicated to all affected personnel immediately.

Lessons have been learned from a variety of safety events caused by MOC deficiencies.
The events highlighted below resulted from changes in equipment, procedures, materials, personnel, and process operations that were not managed well. Had the organizations involved followed a basic change control methodology, they might have been able to prevent the incidents from occurring in the first place. Best practices for managing change are described in H2BestPractices.