Incident scenario development

As part of Process Safety Management (PSM) requirements by both OSHA and the EPA, both risk analysis and emergency response management require the determination (i.e., identification and evaluation) of incident scenarios that are likely to develop at an installation. Risk analyses techniques such as PITA, What-If, HAZOP, etc., will systematically review a process to determine possible deviations from the intended processes that may result in events such as fire and explosions. Additionally, emergency response preparedness plans usually develop creditable scenarios that may develop and the generic responses that are required. These PSM techniques... 

Qualitative reviews are team studies based on the generic experience of knowledgeable personnel and do not involve mathematical estimations. Overall these reviews are essentially checklist reviews in which questions or process parameters are used to prompt discussions of the process design and operations that would develop into an incident scenario of interest due to an identified risk. 

A support system of incident reporting for airline cabin crew was developed. The system was assessed by experiments, where the participants read a test incident scenario created from some past cases and made reports with and without using the support system. In addition, the participants answered a questionnaire for subjective assessment. As a... 

After the incident, an investigation team determined that the first operator had not added the initiator when required earlier in the process. When the relief operator added the initiator, the entire monomer mass was in the reactor and the reaction was too energetic for the cooling system to handle. Errors by both operators contributed to the runaway. Both operators were performing many tasks. The initiator should have been added much earlier in the process when much smaller quantities of monomer were present. There was also no procedure to require supervision review if residual monomers were detected. The lesson learned was that operators need thorough training and need to be made aware of significant hazardous scenarios that could develop. 

Employers must develop in-house capability to investigate incidents that occur in their facilities. A team should be assembled by the employer and trained in the techniques of investigation, including how to conduct interviews of witnesses, assemble needed documentation, and write reports. A multidisciplinary team is better able to gather the facts of the event and to analyze them and develop plausible scenarios as to what happened and why. Team members should be selected on the basis of their training, knowledge, and ability to contribute to a team effort to fully investigate the incident. 

The objective of emergency plaiuiing is to reduce the probability of serious loss due to a particular hazardous accident. The probability of an occurrence of a hazardous accident is first evaluated tlien it is assumed that, if the accident occurs, the worst consequences will follow (the so-called worst-case scenario). Procedures for liandliiig a particular accident are tlien developed and practiced, both to minimize the e.xposure of personnel and to prevent escalation of the origiiuil incident. 

Each event, such as equipment failure, process deviation, control function, or administrative control, is considered in turn by asking a simple yes/no question. Each is then illustrated by a node where the tree branches into parallel paths. Each relevant event is addressed on each parallel path until all combinations are exhausted. This can result in a number of paths that lead to no adverse consequences and some that lead to the incident as the consequence. The investigator then needs to determine which path represents the actual scenario. Generally, a qualitative event tree is developed when used for incident investigation purposes. 

After the most likely scenario has been identified and the logic tree developed, the incident investigation team now reaches the stage of searching out the system-related multiple causes. An accompanying challenge is deciding when to stop further development of each branch of the tree. 

A sample appears in Figure 9-22 on page 219 for a fictitious incident. Developing the matrix is not a one-time exercise, but is usually prepared over the course of the investigation. Gradually, some hypothesis will emerge as more likely and others will become less probable. It is very helpful to others to keep unlikely scenarios on the matrix and document why the scenario was ruled out. Seeing why their pet theory was ruled out can help people accept the team s conclusions. 

Once the timeline or sequence diagram based upon the actual scenario has been developed, the next phase of the investigation involves identifying the causal factors. Causal factors involve human errors and equipment failures that led to the incident, but can also be undesirable conditions and... 

Once the evidence has heen collected, a timeline or sequence diagram developed, and the actual scenario confirmed, the investigation can proceed to the next stage, the identification of causal factors. These causal factors are the negative events and actions that made a major contrihution to the incident. 

Develop a list of potential scenarios and remain open minded. On complex incidents, it is sometimes helpful to develop a list of potential scenarios. Do not fall in the trap of only pursuing the initial obvious scenario. It is important to prove that the actual scenario did happen but it is also important to prove that other potential scenarios did not happen. 

In theory at least, the multi-hit hypothesis can explain the low incidence rate and idiosyncratic nature of DILI. Consider a simple scenario where a particular DILI requires three distinct steps or mechanisms, and the probability of each step occurring in a patient population is <10 percent (or less than 1 in 10 patients). Assuming that the probabilities of these three steps are completely independent of each other, then the overall probability of DILI becomes less than 1 in 1,000 patients. Since a combination of toxicity mechanisms may account for the final DILI, it is imperative that an integrated approach be developed and evaluated to better predict safer drugs. The remainder of this chapter will provide illustrations of such approaches. 

Last, but certainly not least, the recently renewed interest in so-called non-lethal CW threatens to undermine the current prohibition regime and calls into question the viability of any future CW control efforts. If there was the need for a wake-up call to raise awareness of this problem, this was most certainly provided by the use of a fen-tanyl-derivative - as it was called by the Russian authorities - that was used to end the Moscow theatre hostage-taking in fall of 2002.52 However, this incident represents just the tip of the iceberg, as more states than just Russia are interested in utilizing so-called non-lethal chemical weapons in a number of police and military scenarios other than war. Certainly the US military shows a strong interest in developing this kind of capability.53... 

Globally, apart from many national frameworks, various international initiatives have been founded, aimed at the prevention of, and coping with, possible bioterrorism scenarios. In 2006, the U.N. General Assembly released its new counterterrorism strategy. It recommends development of a biological incidents database... 

Release tvoeisl Different accident and non-accident related incidents can be developed to represent the potential route scenarios. 

Flanagan (1954) developed the procedure known as the critical incident technique. This relatively simple process involves interviewing job incumbents and asking for descriptions of critical incidents in their job, and also asking what they did in the particular simation. Critical incident information could also be obtained by supervisors keeping a record of simations they have observed, and employees responses to the simation. Thus, a critical incident represents a specific job simation and a particularly effective response to that simation. The critical incident technique can easily be applied to gather safety-specific examples. A sample of employees would be asked to describe a simation which had a safety aspect and then to describe how the safety issue was handled or resolved. Of course it is necessary to ensure that the response to the simation is indeed the correct response in that it is what the organization would want an employee to do when the particular safety simation occurred. Once a number of these critical incidents have been identified, they can be formed into employment interview questions. The job applicant is presented with the question (or scenario) and is assessed on their description of how they would (or have) handle or responded to the simation, and in particular how... 

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