Human factors situation

With all due respect to the findings of the investigating team, the root cause appears to me to be a human factors situation. The new piping system looked simple but in fact this... 

With all due respect to the findings of the investigating team, the root cause appears to me to be a human factors situation. The new piping system looked simple but in fact this unique system was confusing. A check valve (valve no. 2) was installed on the vent header to prevent cross-contamination. A small block valve (valve no. 4) was installed on the vacuum relief impulse line to provide easy isolation. [5]... 

From a broader perspective, the Abnormal Situation Management Consortium is working to apply human factors theory and expert system technology to improve personnel and equipment performance during abnormal conditions. In addition to reduced risk, economic improvements in equipment reliability and capacity are expected (Rothenberg and Nimmo, 1996). 

In risk characterization, step four, the human exposure situation is compared to the toxicity data from animal studies, and often a safety -margin approach is utilized. The safety margin is based on a knowledge of uncertainties and individual variation in sensitivity of animals and humans to the effects of chemical compounds. Usually one assumes that humans are more sensitive than experimental animals to the effects of chemicals. For this reason, a safety margin is often used. This margin contains two factors, differences in biotransformation within a species (human), usually 10, and differences in the sensitivity between species (e.g., rat vs. human), usually also 10. The safety factor which takes into consideration interindividual differences within the human population predominately indicates differences in biotransformation, but sensitivity to effects of chemicals is also taken into consideration (e.g., safety faaor of 4 for biotransformation and 2.5 for sensitivity 4 x 2.5 = 10). For example, if the lowest dose that does not cause any toxicity to rodents, rats, or mice, i.e., the no-ob-servable-adverse-effect level (NOAEL) is 100 mg/kg, this dose is divided by the safety factor of 100. The safe dose level for humans would be then 1 mg/kg. Occasionally, a NOAEL is not found, and one has to use the lowest-observable-adverse-effect level (LOAEL) in safety assessment. In this situation, often an additional un-... 

Despite the lack of interest in human factors issues in the CPI in the past, the situation is now changing. In 1985, Trevor Kletz published his landmark book on human error in the CPI An Engineer s View of Human Error (revised in 1991). Several other books by the same author e.g., Kletz (1994b) have also addressed the issue of human factors in case studies. Two other publications have also been concerned specifically with human factors in the process industry Lorenzo (1990) was commissioned by the Chemical Manufacturers Association in the USA, and Mill (1992), published by the U.K. Institution of Chemical Engineers. In 1992, CCPS and other organizations sponsored a conference on Human Factors and Human Reliability in Process Safety (CCPS, 1992c). This was further evidence of the growing interest in the topic within the CPI. 

It should be emphasized that the PIFs considered in this chapter, although generally considered important by human reliability specialists, are not meant to be exhaustive in their coverage. Other selections, such as those considered by the methods such as TRIPOD and HP AM (Chapter 2), are possible. It is recommended that the advice of an experienced human reliability or human factors specialist is sought when deciding which PIFs should be covered in a specific situation. 

The human factors audit was part of a hazard analysis which was used to recommend the degree of automation required in blowdown situations. The results of the human factors audit were mainly in terms of major errors which could affect blowdown success likelihood, and causal factors such as procedures, training, control room design, team communications, and aspects of hardware equipment. The major emphasis of the study was on improving the human interaction with the blowdown system, whether manual or automatic. Two specific platform scenarios were investigated. One was a significant gas release in the molecular sieve module (MSM) on a relatively new platform, and the other a release in the separator module (SM) on an older generation platform. 

The final element in management s communication of a desire to reduce human error is the identification and elimination of error-likely situations. Every task is an opportunity for a human error, but some situahons represent greater risks than others. Identifying these high-risk situations is not easy and an expertise in applying human factors principles to the workplace is an essential prerequisite for this identification. Eliminating these hazardous situations is often relatively simple once they have been identified. In some cases it may be appropriate to provide error-tolerant systems, which are those that facilitate identification of and recovery from the errors. 

Rasmussen, J. (1990). Human Error and the Problem of Causality in Analysis of Accidents. In D. E. Broadbent, J. Reason, A. Baddeley (Eds.). Human Factors in Hazardous Situations. Oxford, U.K. Clarendon Press. 

The risk assessment comprises an effect assessment (hazard identification and hazard characterization) and an exposure assessment. The principles for the effect assessment of the active substances are in principle similar to those for existing and new chemicals and are addressed in detail in Chapter 4. Based on the outcome of the effect assessment, an Acceptable Daily Intake (ADI) and an Acceptable Operator Exposure Level (AOEL) are derived, usually from the NOAEL by applying an overall assessment factor addressing differences between experimental effect assessment data (usually from animal studies) and the real human exposure situation, taking into account variability and uncertainty for further details the reader is referred to Chapter 5. As a part of the effect assessment, classification and labeling of the active substance according to the criteria laid down in Directive 67/548/EEC (EEC 1967) is also addressed (Section 2.4.1.8). 

The most relevant study to base a hazard assessment and derivation of a tolerable intake upon is a study that reflects the human exposure situation as well as possible. Eor numerous substances, data are only available from acute (single exposure), subacute (14—28 days), or subchronic (90 days) animal studies. In order to derive, e.g., a TDl or RfD for such a substance, it may be necessary to base the assessment on data from a shorter duration study. An assessment factor allowing for differences in the experimental exposure duration and the duration of exposure for the population and scenario under consideration needs to be considered taking into account that, in general, the experimental NOAEL will decrease with increasing exposure duration as well as other and more serious adverse effects may appear with increasing exposure duration. 

Absolute safety (or zero risk) does not exist for several reasons first, it is possible that several protection measures or safety elements can fail simultaneously second, the human factor is a source of error and a person can misjudge a situation or have a wrong perception of indices, or may even make an error due to a moment s inattention. 

Biocomplexity is a characteristic feature of all systems of the environment connected with life. The ways in which this is manifested are studied within the framework of the theory of stability and vitality of ecosystems. Note that biocomplexity includes indicators of the extent to which interacting systems modify each other, and this means that biocomplexity should be studied by considering both the spatial and biological levels of its organization. The difficulty of this problem is explained by the complicated behavior of the object under study, especially when the human factor is considered, due to which the number of stress situations in the environment is constantly growing. Within this study the Arctic systems are considered as NSS sub-systems. 

Once these questions are answered, the user is led to more detailed questions that address the specific situation. These more detailed questions cover areas such as human factors, communication, training, fatigue, scheduling, environment, equipment, rules, policy, procedure, or barriers to quality. 

Although spontaneous tumors closely resemble the human clinical situation, a number of factors make these models poorly reproducible in controlled settings. These include difficulties in adequately staging the tumors, variations in their natural history, and the low yields of animals that actually develop tumors. Consequently, spontaneous tumors have greater utility in the study of carcinogenesis and chemopre-vention, and are somewhat less useful as routine therapeutic models for studying the treatment of established tumors. 

In this chapter we will emphasize system upsets or abnormal situations where the loss or degradation of components or controls could allow process parameters to exceed the design intent or limit of the process or equipment, resulting in an accidental chemical release. The time factor involved in an operator s ability to assess and correct an operating deviation is discussed in more detail in CCPS Guidelines for Integrating Human Factors into Process Safety Management Systems ... 

As with operating and maintenance procedures, you want the user to use the written EOP to control the situation. Theerefore, EOPs must be accessible and must address the specific needs of the user. From a human factors standpoint, how the EOPs are accessed can affect their use. Here are a few methods to make the EOPs easy to locate and use during an emergency ... 

Requirements development includes both the identification of perceived needs and measurements of real needs. For example, the suit s mask must allow the operator to maintain situational awareness of both surroundings and the protective system status. Development of these systems must be performed in close consultation with the operator community, who provide critical data on human factors as well as appropriate validation and testing procedures. Performance characteristics and threat specifications will require research to optimize the operation and protection factors. This wiU hkely require... 

Jentsch, F., Barnett, J, Bowers, C. A., and Salas, E. (1999), Who Is Hying This Plane Anyway What Mishaps Tell Us about Crew Member Role Assignment and Air Crew Situation Awareness, Human Factors, Vol. 41, No. 1, pp. 1-14. 

The human factors literature is rich in task analysis techniques for situations and jobs requiring rule-based behavior (e.g., Kirwan and Ainsworth 1992). Some of these techniques can also be used for the analysis of cognitive tasks where weU-practiced work methods must be adapted to task variations and new circumstances. This can be achieved provided that task analysis goes beyond the recommended work methods and explores task variations that can cause failures of human performance. Hierarchical task analysis (Shepherd 1989), for instance, can be used to describe how operators set goals and plan their activities in terms of work methods, antecedent conditions, and expected feedback. When the analysis is expanded to cover not only normal situations but also task variations or changes in circumstances, it would be possible to record possible ways in which humans may fail and how they could recover from errors. Table 2 shows an analysis of a process control task where operators start up an oil refinery furnace. This is a safety-critical task because many safety systems are on manual mode, radio communications between control room and on-site personnel are intensive, side effects are not visible (e.g., accumulation of fuel in the fire box), and errors can lead to furnace explosions. 

Endsley, M. (1995). Towards a theory of situation awareness in dynamic systems. Human Factors, 37, 32-64. 

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