Multiple causal factors

Analysis, that can assist with the identihcation of causal factors. The concepts of incident causation encompassed in these tools are fundamental to the majority of investigation methodologies. (See Chapter 3 for information about the Domino Theory, System Theory, and HBT Theory.) The simplest approach involves reviewing each unplanned, unintended, or adverse item (negative event or undesirable condition) on the timeline and asking, Would the incident have been prevented or mitigated if the item had not existed If the answer is yes, then the item is a causal factor. Generally, process safety incidents involve multiple causal factors. 

A process safety incident typically has multiple causal factors. The term direct cause is often used interchangeably with the term causal factor, but this can be confusing because it is also used to refer to just the last causal factor in an incident sequence. 

Once the actual incident scenario is understood and its multiple causal factors identified, this information may be used to determine the incident s root causes. One means of performing root cause analysis involves the use of ready-made, predefined trees. A predefined tree provides a systematic approach for analyzing and selecting the relevant elements of the incident scenario. It is a deductive approach, looking backward in time to examine preceding events necessary to produce the specified incident. 

First, it is necessary to identify the multiple causal factors of the incident. The procedures in Causal Factor Identification may be used to identify tbe causal factors from a timeline or sequence diagram (including a causal factor chart). 

Dose-response models describe a cause-effect relationship. There are a wide range of mathematical models that have been used for this purpose. The complexity of a dose-response model can range from a simple one-parameter equation to complex multicompartment pharmacokinetic/pharmacodynamic models. Many dose-response models, including most cancer risk assessment models, are population models that predict the frequency of a disease in a population. Such dose-response models typically employ one or more frequency distributions as part of the equation. Dose-response may also operate at an individual level and predict the severity of a health outcome as a function of dose. Particularly complex dose-response models may model both severity of outcome and population variability, and perhaps even recognize the influence of multiple causal factors. 

The committee s analysis of the seven chemical events listed in Tables 2-1 and 2-2 showed that there were multiple causal factors for all of the selected events. (Note the committee could detennine causal factors only for incidents for which sufficient investigation data were available.) Rather than being specified for each incident, the causal factors identified by the committee are grouped into the following generic categories ... 

For most all hazards-related incidents, even those that seem to present the least complexity, there are multiple causal factors that derive from less than adequate workplace and work methods design engineering, management and operations, and personnel task performance practices. 

In the hazards-related incident process, deriving from those multiple causal factors ... 

Note the terminology numerous failures, and a series of apparently unrelated breakdowns and errors. An aspect of many incidents that result in severe injury is the cascading effect of multiple causal factors acting in sequence — sometimes in multiple and parallel sequences—toward an undesirable end. 

Multiple causal factors derive from Less Than Adequate design, operations, and task performance practices... 

Too much emphasis caimot be given to the causal factors that derive from less than adequate design decisions. If hazards are not adequately avoided, ehminated, or controlled in the design process, multiple causal factors will originate from those inadequacies. 

Because Multiple Causal Factors Develop—A Hazards-Related Incident May Occur... 

It is the exceptional hazards-related incident that does not have multiple causal factors. This is the process as causal factors develop and an incident occurs. 

Usually, there are multiple causal factors for hazard-related incidents. Yet, there seems to be a desire to retain an age-old theme of simplicity. If people who make incident investigations are directed to select one pertinent fact. .. in each of the specific categories, more than likely that is what they will do. And the value of the investigation is diminished. Where incident investigation is done best, multiple causal factors are sought, and it is the exception when only a single causal factor is recorded. 

INCIDENTS USUALLY HAVE MULTIPLE CAUSAL FACTORS... 

Most incidents will have multiple causal factors. 

Causal factors Enter all of the causal factors (circumstances, events, design of tools, equipment, or the work area, condition of equipment, properties of materials, work methods considerations, management systems, actions or inactions of persons) that contributed to the incident. Almost always, there will be multiple causal factors. 

The immediate major contributor to the occurrence of an incident. A combination of simultaneous or sequential circumstances directly or indirectly contributing to an incident that if they were removed would have either prevented the incident or reduced its consequences. For a typical incident event there are multiple causal factors. Causal factors were formerly called direct causes, key causes, observable causes, and assignable causes. Can be modified to identify several kinds of causes such as direct, early, mediate, proximate, distal, etc. See also Tier Diagramming Root Cause Anafysis (RCA). 

System safety methods assume that accidents and mishaps result from multiple causal factors. System thinking views hazards and causal factors as moving in logical sequences to produce accident events. Traditional approaches to accident prevention simply classify causal factors as unsafe acts and unsafe conditions. Hazard control personnel should use root cause processes to discover, document, and... 

Because employers and safety and health professionals are faced with multiple causal factors for these occupational happenings, they must utilize multiple approaches to prevent the occurrence of accidents and incidents. These range from prevention program development, to behavioral approaches, acceptable best prevention techniques, sophisticated analysis methods, engineering controls, and personal protection for the workers. The approach taken by employers and safety and health professionals will include a combination of prevention approaches that best meets the needs of then-unique industry or business. The approach nsed will be tailored to meet their needs. 

In his speech at the ASSE Symposium, Turner recognized that there are common challenges in applying leading indicators in the practice of safety. He spoke of the conceptual problems since measurement of the effects of the tactics chosen may be difficult. Turner observed that, since there are multiple causal factors for most accidents, choosing the relative leading indicators—the issues for which improvements are to be made in safety management processes— becomes complex. 

For most all reports, causal factors identified were plausible. Citing multiple causal factors was prevalent. References to written job procedures deriving from job hazard analyses or other job study methods were frequent. As in the original study, personnel who had participated in job hazard analyses had a better understanding of causal factors and did a more effective job of investigation. 

Note that in this example, four discrete hazards are shown, with some common causal factors shared by the hazards. Also, note that each hazard has a slightly different outcome, each with a slightly different severity level. Booster crash is not a single hazard with multiple causal factors it is a TLM category that encompasses four related hazards in a family of hazards. 

If a hazard has multiple causal factors that can be ORed together, then there should really be multiple hazards, one hazard for each unique independent causal factor. If a hazard has multiple causal factors that must be ANDed together, then it is a single hazard with multiple causes that must occur together. It should be noted that AND and OR refer to Boolean logic used in FTA. 

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