What is Hazard Analysis?
Hazard analysis is a process used to determine how a system can cause hazards to occur and then reducing the risks to an acceptable level. The process consists of: (1) the developer of the system determining what could go wrong with the system, (2) determining how the effects of the failure can be mitigated, and (3) implementing and testing mitigations.
The analysis must start with the system level and include the component, the user (if any), operator (if any), and environment hazards. Once the hazards are determined and the risk assessment (with predefined quantitative definitions) is assigned, the hazards can be assigned to hardware and/or software as appropriate.
The software hazards are then further broken down into a Fault Tree, which is a top-down approach to determine the functions that cause and the ones that mitigate the associated hazards. At the end of the fault tree analysis, the safety engineer needs to show the risk is lower due to the mitigations in place. The mitigations must be testable in order for the developer to demonstrate to the FDA that they have installed the mitigation and it is effective.
Performing Hazard Analysis
There are several methods available for performing the hazard analysis. The most common types are Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA). Since the software does not have a meantime between failures (MTBF), Ascent has found the FTA method to be superior in the software safety analysis.
Levels of Risk
Ascent uses a three-range process for determining acceptable levels of risk. The three ranges are acceptable, ALARP, and unacceptable, which are defined below:
The determination of how faults can occur requires an individual or team of people with extensive experience in the development of similar types of systems such as real-time embedded systems, PC systems, workstations, or other like processes. Ascent Technologies uses a structured process for the development of software, which greatly enhances the ability of the safety engineers in the performance of hazard analysis.