Hazard analysis

In safety engineering, a hazard analysis is a tool used to characterize the elements of risk. The results of a hazard analysis will drive the methods used for development of a system, both hardware and software. The term is used in various fields of engineering such as avionics, chemical process safety and food safety. Alternative definitions include:

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

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. 

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. 

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.