View source for Hazard analysis

{{Short description|The identification of present hazards as the first step in a process to assess risk }}
<!--Note: Parts of this article are written from the perspective of aircraft safety analysis techniques and definitions; these may not represent current best practice and the article needs to be updated to represent a more generic description of hazard analysis and discussion of more modern standards and techniques.-->
A '''hazard analysis''' is used as the first step in a process used to assess [[Risk|risk]]. The result of a hazard analysis is the identification of different types of hazards. A [[Hazard|hazard]] is a potential condition and exists or not (probability is 1 or 0). It may, in single existence or in combination with other hazards (sometimes called events) and conditions, become an actual Functional Failure or Accident (Mishap). The way this exactly happens in one particular sequence is called a scenario. This scenario has a probability (between 1 and 0) of occurrence. Often a system has many potential failure scenarios. It also is assigned a classification, based on the worst case severity of the end condition. Risk is the combination of probability and severity. Preliminary risk levels can be provided in the hazard analysis. The validation, more precise prediction (verification) and acceptance of risk is determined in the [[Risk assessment]] (analysis). The main goal of both is to provide the best selection of means of controlling or eliminating the risk. The term is used in several engineering specialties, including [[Engineering:Avionics|avionics]], [[Chemistry:Process engineering|chemical process safety]], [[Engineering:Safety engineering|safety engineering]], [[Reliability engineering|reliability engineering]] and food safety.<ref>{{cite web|title=UN Office for Disaster Risk Reduction|url=https://www.undrr.org/|accessdate=26 December 2022}}</ref>

Recent development in computing technology and chemical plant safety enable the use of relevant simulation tools such as [[Computational fluid dynamics|computational fluid dynamics]], fluid-structure interaction analysis and blast effects analysis. Such tools can simulate various scenarios often with high accuracy and reveal areas that can be improved in relation to safety. Real-world applications of such simulation tools to improve safety includes plant hazard, risk and consequence assessment in the chemical, petrochemical, hydrocarbon, oil refinery, LNG plants and all major hazard facilities.
<ref>{{cite web|title=Plant Hazard Mitigation|url=https://www.jimmylea.com/plant-hazard-mitigation.html|accessdate=26 December 2022}}</ref>

[[File:LNG Dispersion Analysis.jpg|thumb|alt=LNG Dispersion Analysis|LNG Dispersion Analysis]]

==Hazards and risk==
A hazard is defined 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 or a functional failure. More often an accident or operational failure 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 or reliability risk can be eliminated, in most cases a certain degree of risk must be accepted. In order to quantify expected costs before the fact, the potential consequences 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.

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 and corresponding functional tasks and work products is the system safety domain are used as objective evidence of meeting safety criteria and requirements.

In 2009<ref>{{cite web |title=Joint Software Systems Safety Engineering Handbook |url=https://www.acqnotes.com/Attachments/Joint-SW-Systems-Safety-Engineering-Handbook.pdf |publisher=Naval Ordnance Safety and Security Activity |access-date=25 August 2021}}</ref> 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 definitions - Safety Related examples==
(aviation)
{| class=wikitable
! Severity !! Definition
|-
| Catastrophic
| Results in multiple fatalities and/or loss of the system
|-
| Hazardous
| Reduces the capability of the system or the operator ability to cope with adverse conditions to the extent that there would be:
* Large reduction in safety margin or functional capability
* Crew physical distress/excessive workload such that operators cannot be relied upon to perform required tasks accurately or completely
* Serious or fatal injury to small number of occupants of aircraft (except operators)
* Fatal injury to ground personnel and/or general public
|-
| Major
| Reduces the capability of the system or the operators to cope with adverse operating conditions to the extent that there would be:
* Significant reduction in safety margin or functional capability 
* Significant increase in operator workload
* Conditions impairing operator efficiency or creating significant discomfort
* Physical distress to occupants of aircraft (except operator) including injuries
* Major occupational illness and/or major environmental damage, and/or major property damage
|-
|Minor
| Does not significantly reduce system safety. Actions required by operators are well within their capabilities. Include:
* Slight reduction in safety margin or functional capabilities
* Slight increase in workload such as routine flight plan changes
* Some physical discomfort to occupants or aircraft (except operators)
* Minor occupational illness and/or minor environmental damage, and/or minor property damage
|-
| No Safety Effect
| Has no effect on safety
|}


(medical devices)
{| class=wikitable
! Severity !! Definition
|-
| Catastrophic
| Results in death
|-
| Critical
| Results in permanent impairment or life-threatening injury
|-
| Serious
| Results in injury or impairment requiring professional medical intervention
|-
|Minor
| Results in temporary injury or impairment not requiring professional medical intervention
|-
| Negligible
| Results in temporary discomfort or inconvenience
|}

==Likelihood of occurrence examples==
(aviation)
{| class=wikitable
! Likelihood !! Definition
|-
| Probable
| 
* Qualitative: Anticipated to occur one or more times during the entire system/operational life of an item.
* Quantitative: Probability of occurrence per operational hour is greater than <math>1 \times 10^{-5}</math>
|-
| Remote
| 
* Qualitative: Unlikely to occur to each item during its total life. May occur several times in the life of an entire system or fleet.
* Quantitative: Probability of occurrence per operational hour is less than <math>1 \times 10^{-5}</math>, but greater than <math>1 \times 10^{-7}</math>
|-
| Extremely Remote
| 
* Qualitative: Not anticipated to occur to each item during its total life. May occur a few times in the life of an entire system or fleet.
* Quantitative: Probability of occurrence per operational hour is less than <math>1 \times 10^{-7}</math> but greater than <math>1 \times 10^{-9}</math>
|-
| Extremely Improbable
| 
* Qualitative: So unlikely that it is not anticipated to occur during the entire operational life of an entire system or fleet.
* Quantitative: Probability of occurrence per operational hour is less than <math>1 \times 10^{-9}</math>
|}


(medical devices)
{| class=wikitable
! Likelihood !! Definition
|-
| Frequent
| ≥ 10<sup>−3</sup>
|-
| Probable
| < 10<sup>−3</sup> and ≥ 10<sup>−4</sup>
|-
| Occasional
| < 10<sup>−4</sup> and ≥ 10<sup>−5</sup>
|-
| Remote
| < 10<sup>−5</sup> and ≥ 10<sup>−6</sup>
|-
| Improbable
| < 10<sup>−6</sup>
|}

==See also==
*Environmental hazard
*{{annotated link|ISO 14971|Medical Device Risk Management - ISO 14971}}
*{{annotated link|Failure mode and effects analysis}}
*{{annotated link|Engineering:Fault tree analysis}}
*{{annotated link|Engineering:Hazard and operability study|aka=HAZOP}}
*{{annotated link|Structured What If Technique|SWIFT}}
*{{annotated link|Engineering:Safety engineering}}
*{{annotated link|Reliability engineering}}
*{{annotated link|Social:Occupational safety and health}}
*{{annotated link|DO-178B|RTCA DO-178B}} (Software Considerations in Airborne Systems and Equipment Certification)
*{{annotated link|DO-178C|RTCA DO-178C}}
*{{annotated link|DO-254|RTCA DO-254}} (similar to DO-178B, but for hardware)
*{{annotated link|Engineering:ARP4754|SAE ARP4754}} (System development process)

==Further reading==

*{{cite book | author=Center for Chemical Process Safety  | title=Guidelines for Hazard Evaluation Procedures, with Worked Examples | edition=2nd | publisher=Wiley-American Institute Of Chemical Engineers | year=1992 | isbn=0-8169-0491-X }}
*{{cite book | author=Bahr, Nicholas J. | title=System Safety Engineering and Risk Assessment: A Practical Approach (Chemical Engineering) | edition=1st | publisher=Taylor & Francis Group | year=1997 | isbn=1-56032-416-3 }}
*{{cite book|author=Kletz, Trevor|title=Hazop and Hazan|edition=4th|publisher=Taylor & Francis|year=1999|isbn=0-85295-421-2}}

==References==
{{Reflist}}

==External links==
* [https://web.archive.org/web/20060407092050/http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl CFR, Title 29-Labor, Part 1910--Occupational Safety and Health Standards, § 1910.119] <br> U.S. OSHA regulations regarding "Process safety management of highly hazardous chemicals" (especially Appendix C).
* [http://www.faa.gov/documentLibrary/media/Order/8040.4A%20.pdf FAA Order 8040.4] establishes FAA safety risk management policy.
* The FAA publishes a [http://www.faa.gov/regulations_policies/handbooks_manuals/aviation/risk_management/ss_handbook/ System Safety Handbook] that provides a good overview of the system safety process used by the agency.
* [http://standards.ieee.org/findstds/standard/1584-2002.html IEEE 1584-2002 Standard] which provides guidelines for doing arc flash hazard assessment.


[[Category:Hazard analysis| ]]
[[Category:Avionics]]
[[Category:Safety engineering]]
[[Category:Software quality]]
[[Category:Reliability engineering]]

{{Sourceattribution|Hazard analysis}}