“The danger which is least expected soonest comes to us.” Voltaire
This article discusses the application of Hazard Analysis, why it is used, and the similarities and differences with FMEA.
Definition of “hazard”
According to NASA System Safety Guidebook, hazard is defined as “any real or potential condition that can cause injury or death, or damage to or loss of equipment or property.”
What is a Hazard Analysis?
“Hazard analysis is the process of examining a system throughout its life cycle to identify inherent safety related risks.” [FAA System Safety Handbook, Chapter 7: Integrated System Safety Analysis, 2000]
A hazard is defined by the Department of Defense in Mil Std 882D as “Any real or potential condition that can cause injury, illness, or death to personnel; damage to or loss of a system, equipment or property; or damage to the environment.”
Put another way, hazards are “unsafe acts and/or unsafe conditions that can result in an accident. An accident is usually the result of many contributors (or causes) and these contributors are referred to as either initiating or contributory hazards.” [FAA, 2000]
What is an example of Hazard Analysis?
The following example of Hazard Analysis comes from the book Assurance Technologies: Principles and Practices, by Dev Raheja. It is a partial example of a Hazard Analysis of a fuel control subsystem.
[Note: the scales for “Criticality” in this example come from Mil Std 882D]
What is the difference between Hazard Analysis and FMEA?
There are many similarities between a Hazard Analysis and an FMEA, and fundamentals of FMEA apply equally to Hazard Analysis. Both FMEA and Hazard Analysis examine functions, failures modes, effects and causes. The primary difference with a Hazard Analysis is that it focuses entirely on safety hazards, whereas the scope of an FMEA covers safety as well as performance, quality and reliability. There are other procedural and worksheet differences.
Since the scope of Hazard Analysis is safety hazards, project teams will need to perform Design FMEA in addition to Hazard Analysis in order to improve the product design, and Process FMEA in order to improve the manufacturing process.
What references and standards are available for Hazard Analysis?
A shortlist of references for Hazard Analysis include:
* ANSI/GEIA-STD-0010-2009, Standard Best Practices for System Safety Program Development and Execution
* FAA System Safety Handbook, Chapter 7: Integrated System Hazard Analysis, December 30, 2010
* FAA System Safety Handbook, Chapter 8: Safety Analysis/Hazard Analysis Tasks, December 30, 2010
* IEEE STD-1228-1994 Standard for Software Safety Plans
* ISO 14971:2007, Medical devices – Application of risk management to medical devices
* SAE ARP4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, 1996-12-01
* Mil-Std 882D, STANDARD PRACTICE FOR SYSTEM SAFETY, 10 Feb 2000
* U.S. Food and Drug Administration, Hazard Analysis and Critical Control Point Principles and Application Guidelines, adopted August 14, 1997, National Advisory Committee on Microbiological Criteria for Foods
* ASTM E2590 – 15, Standard Guide for Conducting Hazard Analysis – Critical Control Point (HACCP) Evaluations
Does Effective FMEAs include information on Hazard Analysis?
Yes. Chapter 15 of my book Effective FMEAs includes application information about Hazard Analysis, including sections on Hazard Analysis and FMEA, Hazard Analysis Procedure, Hazard Analysis Tables and Examples, Hazard Analysis Definitions, and Hazard Analysis References and Standards.
What design precedence guidelines can be used to address hazards?
Various systems engineering books identify hazards based on risk priority, and provide guidance in addressing hazards with an order of precedence:
a. Design the hazard out of the product. If the hazard cannot be eliminated, minimize the residual risk.
b. Design for fail-safe default mode by incorporating safety devices or fault-tolerant features.
c. Provide early warning through measuring devices, software, or other means. The warning should be clear and should attract the attention of the responsible operator.
d. Implement special procedures and training when the above means are unable to eliminate the hazard.
How early in the design process should Hazard Analysis be done?
As with FMEA, Hazard Analysis should be conducted early in the product development process. Hazards should be understood and addressed with specific actions to reduce hazard risk to an acceptable level before the product design is frozen.
Do medical device companies have their own standard for Hazard Analysis?
ISO 14971:2007(E) “Medical devices — Application of risk management to medical devices” includes information on evaluation of hazards, risk evaluation of hazards, and control of hazards for medical devices. Note, this ISO standard refers to risk in terms of severity and probability of harm. FMEA refers to risk in terms of severity, likelihood of failure mode / cause, and detection. These differences need to be understood when using both Hazard Analysis and FMEA.
What is HAZOP?
HAZOP stands for Hazard and Operability Study. It is a structured analysis of a planned or existing process or operation, to identify and possible hazards in a work process. It is similar to Hazard Analysis, with focus on processes.
Hazard Analysis uses its own unique scales. It is a good idea to study the various standards in the list of references (above), and ensure the scales used in the Hazard Analysis are correct for your specific application.
Robust design is used to find the appropriate control factor levels in a design or a process to make the system less sensitive to variations in uncontrollable noise factors. The next article discusses the relationship between FMEA and robust design.