Hazard analysis

Key takeaways

Hazard analysis belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hazard analysis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hazard analysis from memory before moving on to harder problems.

Reference excerpt

A hazard analysis is one of many methods that may be used to assess risk. At its core, the method entails describing a system object (such as a person or machine) that intends to conduct some activity. During the performance of that activity, a potential source of harm (referred to as a “factor” or hazard) may be encountered that could cause or contribute to an occurrence (mishap, incident, accident, hazardous event). Finally, that occurrence will result in some outcome that may be measured in terms of the degree of loss or harm. This outcome may be measured on a continuous scale, such as an amount of monetary loss, or the outcomes may be categorized into various levels of severity e.g. environmental damage, personal injury, or reputational damage etc.

A Simple Hazard Analysis The first step in hazard analysis is to identify the potential source of harm. If an automobile is an object performing an activity such as driving over a bridge, the potential source of harm may be the icy road condition may be icy. If this hazard is encountered, it could cause or contribute to the occurrence of an automobile accident, and the outcome of that occurrence could range in severity from a minor fender-bender to a fatal accident.[1]

Managing Risk through Hazard Analysis A hazard analysis may be used to inform which risk mitigation strategy: probability, occurrence, or outcome to pursue. For instance, the probability of encountering an icy bridge may be mitigated by adding salt such that the ice will melt. Or, a risk mitigation strategy may target the occurrence of the hazard. For instance, putting tire chains on a vehicle does not change the probability of a bridge becoming icy, but if an icy bridge is encountered, it improves traction, mitigating the chance of a sliding into another vehicle. Finally, risk may be managed by influencing the severity of outcomes. For instance, seatbelts and airbags do nothing to prevent bridges from becoming icy, nor do they prevent accidents caused by that ice. However, in the event of an accident, these devices lower the probability of the accident resulting in fatal or serious injuries.[2]

Software Hazard Analysis IEEE STD-1228-1994 Software Safety Plans prescribes industry best practices for conducting software safety hazard analyses to help ensure safety requirements and attributes are defined and specified for inclusion in software that commands, controls or monitors critical functions. When software is involved in a system, the development and design assurance of that software is often governed by DO-178C. 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 the severity of Catastrophic to No Safety Effect. Higher levels of rigor are required for level A and B software with increasing functional tasks and work products. In 2009 a leading edge commercial standard was promulgated based on decades of proven system safety processes in DoD and NASA. ANSI/GEIA-STD-0010-2009 (Standard Best Practices for System Safety Program Development and Execution) is a demilitarized commercial best practice that uses proven holistic, comprehensive and tailored approaches for hazard prevention, elimination and control. It is centered around the hazard analysis and functional based safety process.

Severity category examples When used as part of an aviation hazard analysis, "Severity" describes the outcome (the degree of loss or harm) that results from an occurrence (an aircraft accident or incident). When categorized, severity must be mutually exclusive such that every occurrence has one, and only one, associated severity category. The definitions must also be collectively exhaustive such that all defined occurrences fall into one of the severity categories. In the US, the FAA includes five severity categories as part of its safety risk management policy.

Example medical devices severity categories and definitions when used as part of a comprehensive hazard analysis according to EN ISO 14971:2019 that can be used to presume conformity to the Medical Devices Directive.

Likelihood category examples When used as part of an aviation hazard analysis, a "Likelihood" is a specific probability. It is the joint probability of a hazard occurring, that hazard causing or contributing to an aircraft accident or incident, and the resulting degree of loss or harm falling within one of the defined severity categories. Thus, if there are five severity categories, each hazard may have five unique likelihoods. In the US, the FAA provides a continuous probability scale for measuring likelihood, but also includes seven likelihood categories as part of its safety risk management policy.

Example medical devices likelihood categories and definitions.

See also Environmental hazard – Dangers to or dangers of environments Failure mode and effects analysis – Analysis of potential system failures Fault tree analysis – Failure analysis system used in safety engineering and reliability engineering Hazard and operability study (HAZOP) – Study of risks in a plan or operation Layers of protection analysis (LOPA) – Technique for evaluating the hazards, risks and layers of protection of a system Medical Device Risk Management - ISO 14971 – ISO standard Occupational safety and health – Field concerned with the safety, health and welfare of people at work Reliability engineering – Sub-discipline of systems engineering that emphasizes dependability RTCA DO-178B – RTCA standard for safety-critical software (Software Considerations in Airborne Systems and Equipment Certification) RTCA DO-178C – International aeronautics software standard RTCA DO-254 – Document for guidance of airborne electronic hardware (similar to DO-178B, but for hardware) SAE ARP4754 – Aerospace Practice (System development process) SAE ARP4761 – Aerospace recommended practice from SAE International (System safety assessment process) Safety engineering – Engineering discipline Structured what-if technique (SWIFT) – Method of prospective hazards analysis

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Hazard analysis

Start with the simplest possible case. Write down what Hazard analysis claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hazard analysis before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hazard analysis ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hazard analysis

In research: Hazard analysis appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hazard analysis in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hazard analysis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Avionics, Hazard analysis, Occupational safety and health, so understanding it makes those chapters shorter.
In everyday life: Look for Hazard analysis outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Hazard analysis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hazard analysis means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hazard analysis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hazard analysis in simple terms?

A hazard analysis is one of many methods that may be used to assess risk. At its core, the method entails describing a system object (such as a person or machine) that intends to conduct some activity.

Why does Hazard analysis matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hazard analysis?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hazard analysis.