For potential hazards identified in the work scope, both the severity of consequences and the likelihood of occurrences are considered when ranking the risk of an activity.
Subject Matter Experts (SMEs) as well as the Principal Investigator, equipment designers, researchers and technicians involved in the project, and facilities and line management should be involved in categorizing the hazards and associated risks of the project.
Either qualitatively or quantitatively, each hazard associated with activities in the work scope is categorized (see Step 3), as negligible, low, moderate or high risk.
Both qualitative and quantitative tools are available to assist in determining the level of risk associated with the identified hazards. OSHA 1910.119 gives guidelines for "preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals. These releases may result in toxic, fire or explosion hazards." The standard indicates that a hazard evaluation must be performed and "the employer shall use one or more of the following methodologies:"
- What-If (qualitative)
- Checklist (qualitative)
- What-If/Checklist (qualitative)
- Hazard Operability Analysis (HAZOP)(qualitative)
- Failure Modes and Effects Analysis (FMEA) (quantitative)
- Fault Tree Analysis (quantitative)
- An appropriate equivalent methodology (both)