Hazard analysis

A hazard analysis is a process used to characterize the elements of risk. The results of a hazard analysis is the identification of unacceptable risks and the selection of means of controlling or eliminating them. The term is used in several engineering specialties, including avionics, chemical process safety, safety engineering and food safety. Alternative definitions include:

Identification, studies and monitoring of any hazard to determine its potential, origin, characteristics and behaviour. [1]

The process of collecting and evaluating information on hazards associated with the food under consideration to decide which are significant and must be addressed in the HACCP plan. [2]

An analysis or identification of the hazards which could occur at each step in the process, and a description and implementation of the measures to be taken for their control. [3]

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Hazards and risk

A hazard is defined in FAA Order 8040.4 as a "Condition, event, or circumstance that could lead to or contribute to an unplanned or undesirable event." Seldom does a single hazard cause an accident. More often, an accident occurs as the result of a sequence of causes. A hazard analysis will consider system state, for example operating environment, as well as failures or malfunctions.

While in some cases safety risk can be eliminated, in most cases a certain degree of safety risk must be accepted. In order to quantify expected accident costs before the fact, the potential consequences of an accident, and the probability of occurrence must be considered. Assessment of risk is made by combining the severity of consequence with the likelihood of occurrence in a matrix. Risks that fall into the "unacceptable" category (e.g., high severity and high probability) must be mitigated by some means to reduce the level of safety risk.

When software is involved in a system, the development of that software is often governed by DO-178B. The severity of consequence identified by the hazard analysis establishes the criticality level of the software. Software criticality levels range from A to E, corresponding to severities of Catastrophic to No Safety Effect.

Severity definitions

Likelihood of occurrence

See also

• Hazop
• Safety engineering
• Occupational safety and health
• RTCA DO-178B (Software Considerations in Airborne Systems and Equipment Certification)
• RTCA DO-254 (similar to DO-178B, but for hardware)
• SAE ARP4761 (System safety assessment process)
• SAE ARP4754 (System development process)
• MIL-STD-882 (Standard practice for system safety)

Further reading

• Center for Chemical Process Safety (1992). Guidelines for Hazard Evaluation Procedures, with Worked Examples, 2nd Edition, Wiley-American Institute Of Chemical Engineers. ISBN 0-8169-0491-X. 

• Bahr, Nicholas J. (1997). System Safety Engineering and Risk Assessment: A Practical Approach (Chemical Engineering), 1st Edition, Taylor & Francis Group. ISBN 1-56032-416-3. 

• Kletz, Trevor (1999). Hazop and Hazan, 4th Edition, Taylor & Francis. ISBN 0-85295-421-2.