User:Pbsouthwood/Diving safety and accident avoidance

Dive safety is primarily a function of four factors: the environment, equipment, individual diver performance and dive team performance. The water is a harsh and alien environment which can impose severe physical and psychological stress on a diver. The remaining factors must be controlled and coordinated so the diver can overcome the stresses imposed by the underwater environment and work safely. Diving equipment is crucial because it provides life support to the diver, but the majority of dive accidents are caused by individual diver panic and an associated degradation of the individual diver's performance. - M.A. Blumenberg, 1996

Human error is inevitable and everyone makes mistakes at some time. The consequences of these errors are varied and depend on many factors. Most errors are minor and do not cause significant harm, but others can have catastrophic consequences. Examples of human error leading to accidents are available in vast numbers, as it is the direct cause of 60% to 80% of all accidents. In a high risk environment, as is the case in diving, human error is more likely to have catastrophic consequences. A study by William P. Morgan indicates that over half of all divers in the survey had experienced panic underwater at some time during their diving career. These findings were independently corroborated by a survey that suggested 65% of recreational divers have panicked under water. Panic frequently leads to errors in a diver's judgment or performance, and may result in an accident.

Human error and panic are considered to be the leading causes of dive accidents and fatalities

Only 4.46% of the recreational diving fatalities in a 1997 study were attributable to a single contributory cause. The remaining fatalities probably arose as a result of a progressive sequence of events involving two or more procedural errors or equipment failures, and since procedural errors are generally avoidable by a well-trained, intelligent and alert diver, working in an organised structure, and not under excessive stress, it was concluded that the low accident rate in commercial Scuba diving is due to this factor.

The study also concluded that it would be impossible to eliminate absolutely all-minor contra-indications of Scuba diving, as this would result in overwhelming bureaucracy and would bring all diving to a halt.

Human factors*
Human factors are the influences on human behavior, and the resulting effects of human performance on a process or system. Safety can be improved by reducing the frequency of human error and the consequences when it does occur. Human error can be defined as an individual's deviation from acceptable or desirable practice which culminates in undesirable or unexpected results.

Categories of error
Reason categorizes how errors occur by analysing what causes a plan to fail.
 * If a plan is good, but poorly executed, then failure is due to slips, lapses, trips or fumbles.
 * If the plan itself is faulty, then failure is due to a mistake.
 * If established or approved procedures or regulations are intentionally ignored, then a mistake can be categorised as a violation.

Levels of performance
These error categories relate to three levels of human performance:
 * Skill-based: Routine, practiced tasks performed in a largely automatic fashion, with occasional conscious progress checks.
 * Rule-based: If the automatic responses are unsuitable, a switch of level can be made where memorized performance patterns or rules are applied. These are structured on an If (situation), then do (actions) pattern, often similar to one from previous experienc, and perceptions of the current situation are used to select an appropriate solution from memory. Potential solutions are developed through education, training, and experience, and are selected automatically from memory, but verified that they are appropriate by conscious thought.
 * Knowledge-based: When solutions from memory do not suit the current situation, the fall back is to knowledge-based solutions, where the current situation must be analysed and a solution developed in real time. Performance is relatively slow and laborious and the process is subject to errors resulting from constraints of informarion, time, understanding, intelligence and distractions. During emergencies, well-reasoned responses are often substituted by inappropriate and unsuccessful reactions.

Error mechanisms
Three error mechanisms can be defined which correlate the error categories with human performance levels not, due to inattention, distraction, or simply inadequate ability. failure to apply a good rule. attempt to analyse an unfamiliar problem.
 * Skill-based slips, lapses, and fumbles, where the plan is good but execution is
 * Rule-based mistakes, where a good rule is misapplied, a bad rule applied, or there is a
 * Knowledge-based mistakes, where a cognitive error is made in an

Violations
Violations are a special category of mistakes where someone intentionally fails to apply a good rule, or deviates from acceptable or desirable practice. Four categories of violations may be identified:
 * Routine violations, which involve cutting corners, or taking short cuts, increasing risk for convenience or profit.
 * Violations 'for kicks', where rules are broken to prove machismo or to alleviate boredom.
 * Necessary violations, where the rules prevent people from performing a necessary task.
 * Exceptional violations, which usually are the result of extreme emotions.

Age and gender are factors in the tendency to violate rules: Young men are more likely to violate rules than most older women, but men and women of all ages are similarly prone to error.

These error mechanisms explain the psychological basis for errors, but the mechanisms are not readily observable.

Stress*
Stress has been defined as "the result of an imbalance between the demands placed upon an individual and the capacity of that individual to respond to the demands"

A person will respond to stress by taking actions to change the situation in order to reduce the stress When the actions are successful the result is described as 'coping', when unsuccessful the level of stress will increase and may lead to panic.

The person exposed to a stressful situation (beyond skill based response), cognitively appraises the situation and compares it to previous experience using rule based or knowledge based assessment. The perception of stress is an individual reaction based on learned behaviour and available information and can vary dramatically between subjects. Percieved stress levels can in many cases be reduced by a reduction in uncertainty, which may result from education, training and experience, and a stressor which is percieved by one person as a threat, may be regarded as a challenge by someone else, or an inconvenience by a third person. These perceptions all evoke a response, but they indicate a very different level of tolerance and ability to cope with the situation.

Once stress is perceived, the person must decide how to respond to the stressor. The situation must be assessed, memory interrogated, options evaluated, and an appropriate response chosen.

Ability to perform the chosen response may be affected by the stress situation, and once the response has been attempted, the subject will review how the response has affected the situation, and judge whether the response has been effective.

Depending on the percieved residual stress, the process may be stopped or repeated indefinitely until the situation has been resolved, or the stress level increases until the subject is no longer able to cope.

Performance under stress
The level of perceived stress can affect performance. When there is little stress there is a tendency toward carelessness that may result in poor performance, but sufficiently high stress can overwhelm capacity and cause degraded performance due to inability to cope. Optimum performance occurs when the stress levels are less than the person's ability to respond, but sufficient to keep them alert. This varies with the individual and the situation, and can not be maintained continuously, but performance can be improved through personnel selection and training.

Training
The benefits of training may include an increase in performance at a given stress level and improvement of coping skills by developing response reactions to given stress situations. These are patterns of action which have been learned by experience and can be applied to similar situations, when the person operates on Reason's rule-based performance level, and reduce the need for a long and error prone cognitive process, thereby saving time, reducing stress and improving the ability to cope.

The objective of training should be to improve ability to continue the normal coping process when presented with unforeseen circumstances. A possible danger of training is over-reliance on learned procedures, as each stress situation is in some way unique and therefore no learned procedure will be a perfect match. The individual must retain the ability to assess whether the learned procedure is appropriate and adapt it to the specific situation. Therefore training should include situational assessment and decision making under stress.

Panic
It is important that an individual maintains the ability to process information and make decisions while under stress. An individual sense of control and competence over or within a stress situation is crucial. An out-of-control, over-stressed individual will tend to truncate the coping process and become indecisive, losing the ability to analyze and act. As the stress situation overcomes the individual's ability to cope, panic sets in. Panic establishes a barrier in the stress response model, that prevents the decision process. A lack of action or continuation of an inappropriate ongoing action may lead to errors and accidents.

From errors to accidents
An accident may be defined as an event leading to injury, occupational illness, death, or material loss or damage. Conversely, a near accident will be defined as an event which had the potential to cause injury, occupational illness, death, or material loss or damage, but did not due to some corrective action.

Three critical stages can be identified in the development of an error into an accident:
 * contributing events and conditions, which create the situation in which the error is possible, or increase the probability of it occurring.
 * a direct cause: The action or lack of action which precedes and precipitates the error, and is an essential contribution to the commission of the error.
 * compounding events and conditions, which alter the consequences of the error once it has occurred.

Equipment, procedures, organization, environment, individual factors and interactions between them are the sources of contributing and compounding events and conditions. Analysis of near accidents can be of great value to identify sources of error and allow planning to reduce or eliminate contributing and compounding conditions.

A safety study estimated about a million shortcuts taken per fatal accident. "The fatality is the peak of the accident pyramid. The base of the pyramid is the shortcuts, and in between are escalating levels of near-accidents which could (but too often do not) serve as lessons learned. Blumenberg, 1996" Accident investigations typically focus on the end event, and attempt to erect barriers to similar accidents, such as personal protection equipment, backup equipment or alarm systems. These are intended to prevent the recurrence of similar accidents, and are often effective in this limited goal.

Accidents continue to occur because the majority of the contributing and compounding factors are not addressed. Human behavior and the systems in which people work are too complex to analyse all possible interactions. . A more effective route to accident prevention is to reduce or mitigate the occurrence of human error by focusing on the contributing and compounding human factors that create an environment in which accidents are likely to occur.

Crisis management
Accidents frequently appear to happen unexpectedly because because people failed to recognize the indications of developing crisis which reulted in the accident. A crisis can be defined as a rapidly developing sequence of events in which the risks associated with the system rapidly increase to a hazardous state. The interaction of system factors is complex and often unpredictable, and hazard can accumulate at a rate which varies depending on the system, until corrective action is taken, the hazard dissipates without intervention, or an accident occurs. Although the individual operator is most often responsible for committing errors that cause accidents, it is also often the individual operator who is best placed to recognize the development of a dangerous situation and take corrective action, and this usually happens before the situation escalates into an accident.

The ability of the operator to recognize potentially dangerous situations can be improved by incorporating warning mechanisms into systems, and training can significantly improve their ability to recognize the development of a hazardous situation and take appropriate corrective action in time to return the system to an acceptable level of safety.

Human factors in diving*
Humans function underwater by virtue of technology, as our physiology is poorly adapted to the environment. Human factors are significant in diving because of this harsh and alien environment, and because diver life support systems and other equpment that may be required to perform specific tasks depend on technology that is designed, operated and maintained by humans, and because human factors are cited as significant contributors to diving accidents in most accident investigations

Professional diving is a means to accomplish a wide range of activities underwater in a normally inaccessible and potentially hazardous environment. While working underwater, divers are subjected to high levels of physical and psychological stress due to environmental conditions and the limitations of the life support systems, as well as the rigours of the task at hand.

Unmanned remotely operated vehicles (ROV's) allow performance of a variety of tasks at almost any depths for extended periods, but there are still many essential underwater tasks which can only be performed or are most effectively performed by a diver. A diver is still the most versatile underwater tool, but also the most unpredictable, and his own behaviour may threaten his safety.

Recreational, or sport divers, including technical divers, dive for entertainment, and are usually motivated by a desire to explore and witness, though there is no distinct division between the underwater activities of recreational and professional divers. The primary distinction is that legal obligations and protection are significantly different, and this is reflected in organisational structure and procedures. Both categories of diver are usually trained and certified, but recreational diving equipment is typically limited to Self Contained Underwater Breathing Apparatus (Scuba), whereas professional divers may be trained to use a greater variety of diving systems, from Scuba to surface supplied mixed gas and saturation systems. A recreational diver may use some ancillary equipment to enhance the diving experience, but the professional will almost always use tools to perform a specific task.

Since the goal of recreational diving is personal enjoyment, a decision to abort a dive, for whatever reason, normally only affects the diver and his companions. A working diver faced with the same decision, must disappoint a client who needs and expects the diver's services, often with significant financial consequences. Therefore the working diver often faces greater pressure to provide the service at the cost of reduced personal safety. An understanding of the human factors associated with diving may help the diving team to strike an appropriate balance between service delivery and safety.

Factors in diving
A dive team may be considered as a system which is influenced by the following factors: There are considerations associated with each of these factors relating specifically to diving.
 * equipment
 * procedures
 * organization
 * environment
 * individuals
 * interactions

Equipment
Diving equipment can be grouped into four general categories:
 * Life support equipment - the system that provides breathing gas to the diver.
 * Safety and protective equipment.
 * Equipment that helps the diver adapt to the underwater environment.
 * Specialized tools for performing underwater work.

Manufacturers are continuously improving diving equipment to allow deeper, longer and safer diving operations, but the equipment still has ergonomic limitations and can exert significant stress on the diver: Proper ergonomic engineering can reduce the physical demands on the diver due to the equipment, but it also important for equipment design to consider psychological aspects. Research by Morgan and others has shown that anxiety states may be a response to disordered breathing caused by use of breathing apparatus, and that some people experience respiratory distress or panic behaviour while doing physical exercise wearing scuba. Morgan has also recommended that more research be done on psychological aspects of human-respirator interface.
 * Regulators require increased breathing effort.
 * Protective suits restrict mobility.
 * Fins work muscles differently to walking or running, which are more natural activities for humans.
 * Tools are often bulky, heavy, and physically difficult to move and operate underwater.

Procedures
Diving procedures are promulgated in many forms, including: Among the organisations publishing diving procedures, the US Navy, British HSE and NOAA are notable for funding published scientific research on diving safety.
 * Navy Diving Manuals
 * Training and instructor reference manuals of the recreational diver training agencies
 * Government health and safety regulations
 * Codes of Practice published by government departments, IMCA and other asociations of diving contractors, NOAA and other Scientific diving institutions, Cave diving groups etc.
 * Operations manuals of individual diving companies.

Separate dive procedures are developed for each type of diving, such as air and mixed gas diving, inshore and offshore diving, or recreational and professional diving. Decompression tables, programs and algorithms that prescribe depth and time limitations are also a subset of procedures, and highlight the unique nature of the hyperbaric work environment.

Environment
The underwater work environment exposes divers to physical, psychological and pathological stresses. No other industrial working environment alters normal worker physiology more than diving. Blumenberg 1996 .

Environmental influences include pressure, cold, currents, surge, and limited visibility, and underwater conditions can change rapidly, often without warning. Dive teams must anticipate environmental conditions and their effects, and plan accordingly. The diving environment cannot be controlled, but the diving team can control when and how the diver enters the underwater environment.

Individual
The dominant factor controlling diver safety is the individual diver's physical and mental fitness to dive, and physical and psychological evaluation of divers can improve dive safety.

Not everyone has the physical and mental capacity to dive safely. Professional diving can be physically demanding work, and some diving tasks require considerable strength and stamina, and a sufficient reserve of physical and psychological strength to cope with unexpected situations. The requirements for recreational diving may be less rigorous, but any diver, whether professional or recreational, should have some minimum capabilities in order to dive safely. Physical screening standards which take into account anticipated work demands are commonly used by commercial and military divers, and detailed lists of physical contraindications to diving have been published. These standards can vary widely, but the need for physical screening is generally accepted.

Behavioral problems may be more important than physical problems because 'no amount of physical screening can protect a diver from his own stupidity' and 'the majority of diving accidents are caused by poor judgment or inattention to the basic rules of diving safety... ' Mental fitness may be at least as important as physical fitness for divers. and maturity and responsibility should be evaluated as carefully as physical health and fitness.

Selection of divers should match the individual's mental and physical abilities to job demands, but although research has successfully developed a unique psychological profile for divers, pschological screening is seldom applied. According to Morgan, divers are "characterized by low scores for measures of anxiety, and high scores for measures of aggression, assertiveness, confidence and sensation-seeking; they also tend to possess an internal locus of control." Morgan has also successfully used Spielberger's State-Trait Anxiety Inventory to predict with 88% accuracy which divers amongst a class of new recreational divers would experience panic.

Organization
The organizational factor is the dominant controllable factor affecting behavior of the individual diver. The organization can be analysed at several levels ranging from a two man buddy team through the dive team, the whole organization and up to the whole diving industry, and all organizational levels influence the individual diver's behavior and performance.

Interactions
Interactions between the other factors is the most unpredictable factor. Some interactions are linear and relatively easily predicted, but others are complex. Unanticipated interactions between factors can be critical when a diver is working in an isolated hyperbaric environment. Thorough planning and preparation can help to minimize unanticipated interactions, and effective coping skills may be necessary to control interactions when they occur.

Panic
The most frequently cited cause of diver injury or death is panic, or a loss of control Analysis of the human factors associated with diving can identify the primary influences which lead to panic, and suggest methods to promote safety.

Dive safety is primarily controlled by the individual diver and his ability to cope with stress underwater. The development of a diving accident may begin with a diver in a normal psychological and physiological state. The presence of a stressor may alter the diver's psychological and physiological state, and if the stress becomes excessive the diver's skills will diminish. Stressors may arise from human factors, the environment, equipment, procedures, organizational factors, or interactions between any of these, and these stress effects are cumulative. Normally a diver is able to cope with applied stressors and perform the dive safely. As long as the diver has sufficient capacity for coping, then the stress is relieved or controlled and the operation can continue. If the stress demand exceeds the diver's capacity, then the stressor is beyond the diver's control and an accident may result.

Coping
Appropriate stress response, or coping, is a cognitive process which evaluates a stress situation and the available options, then selects an appropriate course of action to respond. A diver needs to retain the ability to process information and make decisions while under stress, especially when confronted with unforeseen events. The diver's maxim, "stop, breathe, think, act", is a widely taught method for working through unexpected events underwater. The intention is to calm the diver and maintain an ability to cognitively appraise a stress situation.
 * 1) Stop any action which may have created or is exacerbating the stress situation. This is intended to stabilise the situation sufficiently for the subsequent steps to be effective.
 * 2) Focus on breathing effectively, concentrating on breathing rate and depth, and relaxing as much as possible. Experience shows that the majority of diver fatalities are due to drowning even though ample air was still available to the diver. This step should calm the diver's rising anxiety by showing him that adequate life support is on hand, and counteract any carbon dioxide buildup that may be contributing to anxiety.
 * 3) Think about the problem. Assess the situation and evaluate the options for resolving the imposed stress. At this stage the diver is probably operating in Reason's knowledge-based performance level where training and education can provide tools to help solve the problem.
 * 4) Select a preferred option and act. This completes the stress response process. If the response has the desired effect, the situation should resolve, otherwise further thought and another response will be needed.

The dive maxim, "stop, breathe, think, act" is generally a good response, but it is not appropriate for all diving emergencies. This response assumes that both time and an adequate supply of breathing gas are available, and though this is often true, some situations require immediate learned responses which must be habituated by education, training and repetitive practice to overcome inappropriate instinctive and natural reflexive responses. For example, a diver should exhale whenever ascending to prevent lung overexpansion injuries, and if the diver is subject to a collision or sudden upwelling underwater, the natural reaction may be to tense up and hold his breath, particularly if the breathing gas supply is interrupted at the same time. This reaction could prove fatal if the diver is lifted sufficiently to cause lung overexpansion. Only through education training and practice, and perhaps proper selection, will the diver reflexively exhale as a response to a pressure reduction. Other factors suggested by Bachrach to prevent panic are listed below: Psychological tests?
 * 1) Physical fitness: having a reserve capacity.
 * 2) Training which emphasizes in-water skills and comfort
 * 3) Medical examinationss to ensure no hidden contraindications to diving
 * 4) Fatigue prevention or avoidance
 * 5) Age limits

Temp edit point
While dive safety is foremost a function of the individual diver's performance, it is the diver's organization which exerts the dominant and controllable influences affecting the diver's penormance. The organization often controls the multiple influences acting upon the diver, and organizational factors (such as culture, regulations, structure and supplies) are responsible for the majority of contributing and compounding events leading to accidents. It is important that the individual diver is part of a team which can help him cope with unforeseen circumstances. Methods are needed to help organizations exert positive, rather than detrimental, influence on the diver.

Organizational research into the characteristics of High Reliability Organizations, and Crew Resource Management systems as used by the airline industry can help to improve organizational factors on two different levels. The work on High Reliability Organisations looks at the organization as a whole, while Crew Resource Management focuses on team development within an organization.

Background
Many modern organizations operate in hazardous and uncertain environments which have the potential not only to harm employees, but also cause catastrophic harm to the public and surrounding ecosystems. Examples of such organizations include a nuclear power plant or oil refinery. Modern technology has magnified man's ability to do work, but it has also magnified the potentially negative consequences of that work. In organizations where the consequences of an accident can be catastrophic, accidents are intolerable. Consequently, errors that could potentially lead to an accident are unacceptable. Fortunately, many potentially hazardous organizations operate nearly error and accident free, and these organizations have been labeled as High Reliability Organizations (HRO's).

Organizational researchers have defined high reliability organizations as "technologically complex, potentially hazardous organizations in which accidents can be catastrophic to the organization and/or society as a whole, but operate nearly accident free". A good example is the U.S. air traffic control system, where controllers handled over seventy million aircraft flights during the 1980's without a single mid-air collision. Other HRO's which have been studied in depth include Pacific Gas & Electric (PG&E), and the US Navy's aviation program. The product of this research is a list of oiganizational characteristics that promote reliability, and challenges to some common theories of organizational design.

High reliability characteristics are useful for dive operations even though dive teams do not strictly meet the definition of a 'high reliability organization'. While diving is certainly technologically complex and potentially hazardous, errors would rarely be considered catastrophic to the public or environment. Errors committed underwater, however, can lead to fatal consequences for the individual diver. Therefore, this study strives to improve dive safety by applying the results of research into high reliability organizations.

High Risk Systems
High reliability organizations must overcome two characteristics common to high risk systems: complex interactions and tight coupling. According to Perrow, interactions between system components or procedures can be either linear or complex. "Linear interactions are those in expected and familiar production or maintenance sequence, and those that are quite visible even if unplanned. Complex interactions are those of unfamiliar sequences, or unplanned and unexpected sequences, and either not visible or not immediately comprehensible". While linear interactions dominate in a system, it is the complex interactions which often have the potential for catastrophic consequences. High reliability organizations, therefore, must somehow compensate for these complex interactions.

Social scientists use the term 'coupling' to describe the strength of relationships within an organization. Loosely coupled systems have loose connections. Tightly coupled systems, on the other hand, are characterized by time dependent processes, invariant process sequences, invariant production goals, and little slack. Time-dependent processes cannot wait for attention. Invariant processes must be completed in an expected sequence, e.g. B must follow A; and invariant production goals allow only one general production method. Little slack does not allow for any variance from expectations. In general, tight coupling implies a lack of flexibility within the system and its operating procedures. HRO strategies work to control processes, but retain enough flexibility to adapt to unforeseen events.

Characteristics of High Reliability Organizations
Research on high reliability organizations has produced a common list of characteristics which help the organization to overcome the complex interactions and tight coupling common to high risk systems, and allows the organization to reduce risk and promote reliability.

These characteristics are also appropriate for organizations emphasizing safety, and include:
 * Focus on reliability
 * Adaptive organizational structure
 * Accurate decision making
 * Training
 * Flexibility within formal rules
 * User-friendly human-system interfaces
 * Process auditing
 * Redundancy
 * Senior management
 * Culture of reliability

Focus on reliability
The dominant characteristic of every HRO is a long-term focus on reliability. Reliability pervades every aspect of the organization, including personnel, equipment and procedures.

Adaptive organisational structure
The majority of High Reliability Organisations that heve been studied have normally hierarchical structures, but can rapidly assume a decentralized structure when facing a potential crisis. The formal hierarchy helps the organization to keep on track during normal operations, while the decentralization adaptation allows flexibility and expedited decision making in stress situations.

Accurate decision making
Accurate and timeous decisions under both normal and stressful circumstances are necessary for operational reliability. . In order to allow decisions to be both accurate and in time to be effective, the decisions should be made by the most qualified available decision maker for the situation. This implies that the information and requirement for the decision gets to that person in time for the decision to be made and implemented before the situation escalates. When rapid decisions are required in high reliability organizations, the decision is most likely to be made at the point of problem sensing, normally at the operator's level. Normal daily operating decisions are also made at the operator's level; while strategic decisions are pushed up to higher managerial or executive levels.

Decisions may be referred to the most experienced or qualified person in the organization. Good decisions rely on sufficient accurate information available in time, and this requires an effective communications system. In the case of professional diving, communications between diver and surface team allow the supervisor to make appropriate decisions regarding safety and productivity with minimum delay, and the requirement for a diving medical consultant on telecommunications stand-by during diving operations helps effective management of medical emergencies.

Training
High reliability organisations tend to conduct ongoing training, not only to improve performance under normal circumstances, but also to improve decision making skills as a preparation for crisis response.

It is easier to control the effects of an error if it is recognised early and corrective action is taken without undue delay. Training which is focused on areas where critical errors can occur can improve the skills for early recognition of these errors, provide a knowledge and understanding of how to prevent the errors from developing into accidents, and improve the ability to cope effectively with stress and the consequences when it is not possible to prevent an accident.

Flexibility within formal rules
Research has indicated that formal rules and procedures help mitigate risk if they are followed and enforced when appropriate to the situation as they keep an organization on track during normal operations by facilitating rapid and reliable response to anticipated situations. When faced with a unforeseen crisis, formal rules may not apply and can lead to disaster if followed when inappropriate. Under these circumstances the organization must allow for flexible and reactive response.

User-friendly human-system interfaces
Some equipment is designed taking little account of the interaction between equipment and operator, but this can lead to problems as most accidents occur during system operations and are caused by people. Human Factors Engineering and ergonomics are important: equipment design and procedures must recognize human limitations, and the extent of automation should consider the needs of the operator.

Process auditing
High Reliability Organisations use internal and external auditing of their processes to identify sources of problems and ensure rules are followed. Audits provide a system of checks which keeps the process on target, and promote early detection of errors. Independent checking is especially valuable because it brings untainted views. Thus, the adverse effects of errors are detected and corrected before they escalate into an accident.

Redundancy
Redundancy in people, equipment, and procedures strengthens the organization so that it can survive minor errors. The organization cannot afford to act like a chain, which is only as strong as the weakest link. Within an organization, redundancy can be achieved in two ways: through duplication and overlap. Duplication provides two or more units performing the same tasks, such as back-up pumps. Overlap implies that neighbors can cover for neighbors, or each man knows the job of the man directly above and below. If a person is lost, someone can step in without a significant loss to the organization. Additionally, redundant monitoring increases the likelihood that an error is detected early and corrective action is taken quickly before it escalates into a larger problem.

Senior management
The role of senior management in High Reliability Organisations is strategic planning and to help the various parts of the organization obtain the information and resources they require.

Culture of reliability
Culture can be defined as the shared norms and values of a group, or simply as "the way we do things here". Once in place, it is difficult to change the organization's culture, but change may occur through a continuous and gradual process. Organizational culture pervades all other high reliability characteristics, and it is the lynch pin which holds the organization together. The organizational culture establishes behavioral norms by rewarding desired behavior and punishing inappropriate behavior. Rewards and punishment are the links between authority, responsibility and accountability within the organization. If an individual is given a responsibility, then he must also be given commensurate authority within the organization to fulfill his responsibility. Finally, the individual is held accountable through rewards or punishment. In HRO's, reliability is rewarded.

Combating High Risk
The combination of characteristics of high reliability organisations helps reduce high risk by reducing the effects of complexity and tight coupling..

Complex interactions are managed by: * User-friendly human-system interfaces minimize perceived system complexity. * Training helps prepare operators to cope with unexpected events, and improves their decision making. * Accurate decision making ensures the response is appropriate. * Redundancy ensures there is more than one means to respond to unexpected events.

Tight coupling is managed by: * Allowing flexibility within the organization's structure and formal rules. * Front-line personnel are given the authority to respond as necessary, and the organizational culture holds them accountable for their actions. * Reliability is promoted by rewarding reliable behavior. * Senior management and continuous process auditing monitor the system and ensure it maintains its focus on reliability

Crew Resource Management
Crew Resource Management (CRM) is a training methodology which promotes team reliability through development of interpersonal skills. Originally developed for the airline industry, CRM is ideal for any environment where people must interact with technology and each other. It has recently been successfully exported to military aviation, hospital operating rooms, nuclear power plants and corporate management. This study proposes that CRM principles be applied to working dive teams.

The necessity of CRM is illustrated by two points. First, the successful operation of complex, high tech systems usually requires a cohesive team. Second, both the human and machine elements of that system have performance limits. Optimal performance is achieved when both people and equipment operate within their limits. Performance degrades when people or equipment operate outside of these limits. Engineers have long recognized equipment limitations. Organizations, however, are only beginning to recognize the limits of the human elements. This recognition of human factors is crucial according to Helmreich because research into accidents and adverse incidents has shown that the majority involve human error. Perhaps more significantly, the errors by humans tend to fall in the areas of team coordination and communication, leadership, and decision making. Thus, exceeding perlormance limits causes breakdowns within the team, which leads to system accidents.

The goal of CRM is to reduce the frequency and mitigate the consequences of human errors. The CRM goal can be seen as a multilayered pyramid. The entire pyramid represents all the errors which a team may commit. CRM strives to prevent the majority of these errors, represented by the bottom layer of the pyramid. Since human error can never be completely eliminated, CRM also strives to contain the effects of errors which do occur, and these errors are represented as the pyramid's middle layer. Containment prevents the rapid escalation of an error into an accident. Finally, if accidents do occur, CRM principles help to mitigate the consequences. This is represented by the tip of the pyramid. Recall that the one accident represented by the tip of the pyramid is typically preceded by one-million unsafe acts at the base of the accident pyramid. If we can learn from these unsafe acts and near accidents, then fewer accidents should occur.

CRM strives to reduce human error by understanding the relationship between human performance and stress. It is imperative that the organization recognize the inevitability of human error, and the relationship between error and stress. Stress should be recognized as a component of all human effort, and not as an individual weakness. An individual's willingness to acknowledge the effects of stress on his or her performance is subject to influence from the national, organizational and professional cultures. Organizations which must operate accident free must encourage their members to admit fallibility and acknowledge the effects of stress. The organization should adopt non-punitive policies regarding everyday error. This does not suggest that organizations accept the consequences or become tolerant of violations.

Training is a means to improve individual competence under any given stress level. Crew resource management requires that members are competent in their individual skill requirements before they start team training, which is focussed on improving team coordination through development of interpersonal skills. This approach has been validated by the positive results recorded in commercial aviation and within NASA.

Improving dive safety
Efforts to improve dive safety can take many forms - such as incremental improvements in dive equipment, continued training, or improved depth-time algorithms. This paper has argued that the most significant improvement in dive safety can be gained by focusing on human factors and eliminating sources of human error within diving. This assertion is affirmed through expert opinion and dive accident data. If this premise is accepted, then a set of practical tools is necessary to implement human factors awareness in daily dive operations. Such human factor tools must decrease the probability of human error and the effects of errors that do occur. This can be accomplished by managing the contributing and compounding conditions associated with system factors: environment, equipment, procedures, organization, individuals and interactions. • Environment. The underwater environment exerts significant physical and psychological stress that is beyond the diver's control. Divers, therefore, must identify the unique environmental conditions (depth, temperature, etc.) and potential hazards (dangerous marine life, strong currents, etc.) and plan the dive accordingly. The plan must include contingency responses for low probability, but high consequence accidents. Thus a thorough dive plan can mitigate environment stressors. The dive plan must also address equipment and procedural factors, as well as individual and organizational factors. • Equipment. Dive equipment, especially life SUppOlt equipment, also exerts significant stress on the diver. Research and development must continue to improve equipment ergonomics and physiological SUPPOlt. Also, new equipment designs should emphasize robustness and simplicity in design and operation. In the field, equipment considerations are focused on selection, maintenance and usage. Selecting the right tool for the job at hand is crucial for diver's working remotely in an alien environment. Maintenance is also crucial, especially with life support equipment, to ensure the equipment functions as planned when needed. Finally, the diver must be trained to use the equipment properly. These critical equipment decisions reflect procedural, individual and organizational factors. • Procedures. Diving rules and regulation allow an inherently hazardous operation to be performed safely. Rules, however, are only valuable if they are understood and abided by. The organizational culture often determines whether rules are followed or violated. • Organization. Divers almost always function a~:membersof teams, and the team's organizational culture exerts significant influences on individual behavior and performance. Dive planning was discussed earlier as a means to identify potential hazards and mitigate risks, but the dive plan is only effective if it is implemented successfully. The old adage holds true: plan your dive and dive your plan. TIle culture of the team will determine the thoroughness of the plan and the effectiveness of its implementation. The desired characteristics of High Reliability Organizations and the techniques of Crew Resource Management can help ensure that the organizational culture emphasizes safety. • IndivIdual. In field operations, all the previous factors are manifested in the actions of the individual operator. Therefore, the individual is the primaly focus of human factors efforts to improve dive safety. • Interactions. Interactions are often unforeseen, and are best combated by developing simple, yet robust systems and procedures with loose correlations and redundancy. Also, individual divers must maintain a reserve of physical and emotional strength that will allow them to cope with unexpected interactions. Human considerations should be incorporated into all of the above factors. Two factors, however, demand special emphasis because they are the most controllable factors, yet are often the factors that are most out of control. Human factors in diving should focus on two controllable areas: first, improving individual awareness of human factors and ability to cope with stress, and second, improving team coordination, reliability and culture.

Improving individual performance under stress
Individual performance under stress situations can be improved by incorporating human factors into initial selection, qualification and follow-up training. Initial diver training should include human factors awareness. Divers must learn their limitations. There is more to this than teaching depth and time limitations. This includes teaching new divers that each individual has unique limitations. Divers must be aware of their own physical and psychological abilities to cope with applied stressors, and recognize when their performance begins to degrade due to excessive stress. Initial training must also teach new divers how to cope with stress in the working environment. This is typically initiated in the controlled underwater environment of a pool, and then transitions to actual open water conditions. The controlled environment allows instructors to simulate high stress conditions without excessive risk.

This high stress training is a common component of military dive training and most commercial training, but not recreational training. The high stress training is important because it teaches the individual diver how to cope with stress. When the in-water training transitions to open-water conditions, the instructor typically does not impose high stress on the new diver. Instead, the environmental conditions add new stress to the diver, teaching him new coping skills.

Coping skills, like any other skill, must be maintained through continuous training and experience. Typically, real-world experience helps the diver develop response templates to stress situations and additional high stress training is not required. Whenever a new dive environment or piece of dive equipment is introduced, however, work-up training should be done to acclimate the diver and allow for the development of response templates.

Implementing human factors into dive teams
Dive teams should strive to reflect the characteristics of High Reliability Organizations and possess a pervasive focus on safety. Crew Resource Management techniques can help develop these desired organizational characteristics in a team. The aviation and space research center at the University of Texas suggests a four phase approach to CRM implementation that can be adapted to successfully implement human factors into dive teams. 1. Diagnose the organization and define areas of concern regarding human factors. 2. Develop a performance based human factors training program tailored to reflect the organization's specific needs, culture and personnel attitudes. 3. Evaluate and validate the effects of the training through participant feedback and empirical follow-up analysis of the team's performance. 4. Continue training and reinforcement of desired behaviors.

Diagnose the organization
Diagnosing an organization is analogous to a medical diagnosis developed during an annual physical examination. The medical examination is conducted in four stages. The first stage is identifying the person to be examined. The second stage is evaluating the patient's health using information obtained through an extensive medical history questionnaire, a listing of the patient's complaints, and a preliminary examination conducted by nurses to obtain the patient's temperature, blood pressure, and other vital signs. During the third stage, the doctor evaluates all the information and identifies specific areas of concern. This third stage is conducted before the doctor ever examines the patient. The fourth stage occurs when the doctor physically evaluates the patient in the examination room. During the examination, the doctor focuses on areas of concern identified earlier. The doctor asks the patient questions about items written in the medical history questionnaire, and about complaints, examining those areas more closely. The doctor then makes an initial diagnosis, but also orders additional tests to confirm his diagnosis. The doctor may prescribe medication, if necessary, while awaiting the test results to confirm his initial diagnosis. In this medical example, the interaction between the doctor and the patient is crucial for proper correct diagnosis and treatment. The doctor has the medical knowledge to make a diagnosis based on the information provided; however, only the patient knows his body and he must articulate what ails him. Incomplete or incorrect information can lead to a misdiagnosis. Therefore, it is crucial that accurate information is obtained from the patient (the true expert regarding his body) on how his own body feels. It is important to note that the doctor works with a range of subjective values instead of an exact number when evaluating a patient. The doctor looks for trends in these values to determine if a condition is improving or deteriorating.

The medical examination analogy can be translated into a methodology for diagnosing an organization, with three notable exceptions : • The organizational diagnosis should be team based rather than individual. This emphasizes that safety and operational effectiveness are team responsibilities. • The diagnosis should include observations of real operations since statistically the majority of accidents occur during operations, and team member behavior is often inconsistent between training and real operations. • The diagnosis should focus on behaviors implicated in accidents rather than on technical proficiency. The intent of the diagno~s is to identify the presence of behavior that is known to be a contributing or compounding factor in accidents. It is this behavior which leads to degraded performance and technical errors. Thus, the diagnosis focuses on the root causes of accidents. It should be noted that similar behavior-based safety programs have been used successfully in such high risk companies as DuPont to achieve impressive break-throughs in safety. Diagnosing a dive team starts by identifying the organization and selecting expert evaluators. Just as a doctor is a recognized expert in physiology, the evaluators used to diagnose a dive team must be expert divers. Next, detailed information about the team is gathered. Administrative records listed in table 6 should be reviewed, and the material condition of critical equipment should be inspected. Records from any significant events, either positive or negative, should be reviewed. Information should also be gathered by interviewing team members regarding safety during team operations. From this information, areas of concern regarding the team's operations can be identified. The final step in the initial diagnosis is to observe field operations, focusing on previously identified areas of concern and behaviors implicated in accidents.

CRM has enjoyed notable success improving aviation safety by focusing on observable behavior during operations. CRM's expert observers record targeted behaviors that are known to precede errors and accidents on a checklist (called the Line/LOS Version 4). Checklist data and comments are later used to critique crew performance. Differences between desired performance and observed performance can define learning objectives for performance based training. In order to capitalize on the CRM's success, the CRM checklist has been adapted for dive teams. The resultant diving human factors checklist focuses on observable behavior which data and experience have shown precedes dive accidents. The checklist should prove useful in the initial diagnosis of a dive team's human factors awareness and abilities, and in accident investigations to help identify the compounding and contributing behaviors which lead to the accident. The checklist and instructions for its use are provided as appendix A.

Training program development
Human factors training starts with awareness and acceptance of stress as it impacts performance. Specific behavioral techniques which can help reduce the likelihood of an error are taught to counter the influence of stress and reduce error. These techniques are listed in Table 7. Once individuals understand the relationship between stress and performance, CRM transitions to team training in a simulated operational environment and focuses on development of effective interpersonal skills. Team training should be tailored to the specific organization and focus on areas of concern identified during the initial diagnosis of the team.

Cross-checking Preparation Planning Vigilance Verification of communication Speaking up to express concerns Sharing a mental model of the situation Table 7: Individual behavioral techniques to reduce error

Evaluate training
Immediately following the training, the relevance and impact of the training should be measured through participant feedback. These feedback should be used as lessons learned to improve the training. Follow-up analysis ofteam performance should be done to identify trellds in the teams performance.

Reinforcing human factors skills
Human factors skills are primarily interpersonal skills which allow individuals to work effectively as team members. Just like any physical skill, interpersonal skills must be practiced and continually reinforced to remain most effective. VonDerLinn (1995) has identified the top three barriers to successful training that the organization should address in order to reinforce training objectives: 1. Lack of reinforcement on the job; 2. Interference from the immediate work environment; 3. Non-supportive organizational culture. VonDerLinn also recommends the following measures to overcome training barriers: 1. The organization must reward safety and reliability over production, schedule, or cost. 2. Company policy must be rewritten to reflect new attitudes. 3. All levels of the organization must support training goals.

Accident Investigations
The Human Factors in Diving Checklist (Appendix A) was developed primarily to record behaviors during real time observations of dive operations. The checklist, however, can also be useful during post accident investigations to record targeted behaviors. The checklist was so employed to evaluate a U.S. Navy dive accident that resulted in a diver fatality attributed in part to human error. The checklist was used to review a first-hand account of the accident and identify targeted behaviors. The results show whe.re human factors acted as contributing and compounding events that lead to errors and eventually a fatal accident. The following sections summarize the first-hand account of the 1974 fatality. Contributing and compounding events are identified, and then correlated to the Human Factors in Diving Checklist. The resultant scores from the checklist are provided and evaluated. Finally, conclusions regarding the checklists usefulness as a post-accident investigation tool are offered.

Risk identification techniques
Fault tree analysis (FTA) and Failure modes effect criticality analysis (FMECA) are relatively easy to use formal risk identification and evaluation techniques which may be useful to diving experts who are not specialists in risk analysis.

Fault trees can be useful to visualise and estimate the contribution of human factors to a serious end event in diving. Analysis indicated that pre-dive checks are probably the most important issue followed by maintenance and training, and that the use of checklists should be adopted.

These procedures are not necessarily appropriate to evaluate the cause of diving fatalities, which are frequently a sequence of several unrelated events.

Fault tree analysis: Methodology
Fault tree analysis is just one technique for risk identification and assessment. It can be used to show the importance of human factors to the ultimate safety of divers. The fault tree is also used to quantify the differences with differing equipment configurations.

The methodology to perform a fault tree analysis (FTA) with the top event being a ‘dead diver’ is described. The topology developed for this particular FTA is explained. Each branch of the tree is evaluated until an end termination is reached which is attributable to a human factor event such as poor training, poor pre-dive checks or poor maintenance. The value of understanding the significance of these events is then described in detail. In addition, stress, design and accident investigation is discussed in relation to the fault tree.

FTA is a form of 'top down' analysis, in which the culminating event for the analysis is chosen, and possible mechanisms for this event are listed with boolean logic relationships to the event. Conventional Boolean logic symbols may be used for simplicity. Two or more mechanisms which can lead to the event if any one of them occurs, are connected by a logical 'OR' condition, and if both (or all) must occur, the relation is a logical 'AND' condition.

The 'OR' condition does not provide any obstacle to propagation of a failure up through the fault tree, as any of the alternative conditions will lead to the result. The 'AND' condition, on the other hand, creates a barrier, as more than one event must occur together for the fault to propagate. (principle of redundancy)

The exact topology of the fault tree will depend on the analyst, but the end result should be similar if the same items are considered. There are a large number of possible items which may be considered in most fault trees, and it is usually necessary to make some assumptions on initial conditions, and whether some items may be excluded from the analysis.

It is likely that several branches may terminate in common conditions. In diving for example, poor planning, poor pre-dive checks or inadequate training are frequently found to be the cause of a failure, either alone or in combination.

The results of a fault tree analysis may be used in several ways.
 * Pre-dive checklists can be compiled to improve reliability of pre-dive checks
 * Items which can not be adequately tested during a pre-dive check can be put on a suitable maintenance schedule, where appropriate testing is enforced.
 * Faults which have no obstacle to propagation in the tree can be mitigated by configuration or procedural changes, or by use of more reliable equipment. Ideally there should be no unblocked propagation path for a single point of failure. Where this is not reasonably practicable, the risk must be acceptable.
 * Probability of failure can be calculated for any higher level node based on known probabilities for contributory failures.

Failure mode and effects criticality analysis: Methodology
Failure mode and effects and criticality analysis (FMECA), also known as Failure mode and effects analysis (FMEA) may be used to carry out a formal risk assessment on diving life support hardware.

The methodology to perform a failure mode and effects criticality analysis (FMECA) is also described. Both a high level and low level FMECA are given with associated frequency and criticality estimates, together with the resultant risk matrix. A hardware approach is taken and demonstrates that SCUBA equipment is safe if serviced and maintained properly.

Recommendations
1. Dive accident data should be collected for the professional dive community as well as the recreational diving community. This data should track the presence of specific observable behaviors that are known to contribute to dive incidents and accidents. 2. Accidents attributed to 'human error' should be further categorized according to observed behaviors which directly caused the accident (e.g., mistake, slip, violation, ignorance, communications, planning, selection, limitation, preparation, training, or impairment). 3. Initial training for all divers should include formal classroom discussion of human factors. High stress situations should be simulated in a controlled environment to promote the development of coping skills underwater. 4. Dive teams should be regularly assessed for human factors effectiveness. A hecklist could be used as a tool to guide human factor evaluations of dive teams. 5. Periodic training in human factors should be offered to reinforce human factors skills. 6. Risk can be reduced by using pre-dive checks, maintenance and training to minimise the effects of human failure. It is recommended that checklists are adopted, emergency drills practised routinely and design of equipment configuration used to minimise confusion. FMECA provides a way to prioritise risk reduction in diving equipment.

Categories of non-technical skills

 * Situational awareness refers to the behaviors by which members of the team develop a shared mental picture of situations and use these models to provide a common understanding.
 * Decision making refers to selecting the procedures for carrying out a task and reviewing the outcomes of a choice to assess whether the goal has been accomplished.
 * Communication is the mechanism that links the teamwork components to share information among team members.
 * Supervision/leadership includes the direction and structure provided by both the leader and other team members. Monitoring and managing team performance is critical for effective team performance (14,15). The most commonly used subcategories were those of maintaining standards, planning and coordination (7).
 * Team cohesion is concerned with behaviors indicating a sense of “teamness” among team members.
 * Personal resources refers to any personal factors that influence an individual’s level of performance.

Causality of non-technical skills failures
(I)t would appear that as in other high reliability industries, failures in non-technical skills are causal in diving accidents and near-misses. Further, divers also recognize that failures in non-technical skills are significant contributors to diving accidents and near-misses. O'Connor, 2007

Safety culture
Cooper defines safety culture as "that observable degree of effort by which all organizational members direct their attention and actions towards improving safety on a daily basis"

Accident analysis
The collection of accurate accident data is important for the improvement of industrial safety. Reason identifies four critical elements of an effective safety culture — a reporting, just, flexible, and learning culture

Near-miss reporting
As operations become safer, and the number of accidents becomes lower, accidents cease to be a useful metric of performance. Other high-risk organizations (including Royal Navy diving) track near misses — unplanned sequences of events that could have caused harm if existing conditions had been different or had been allowed to progress. Research in other industries suggests that as many as 600 nearmisses may occur for every 10 minor injuries, and one serious injury

For a near-miss reporting system to be used there must be a culture of reporting within the organization. There must be support for the system at both the senior manager and supervisory levels. For members of an organization to submit information about a near-miss, it is important to implement a policy not to punish the individuals involved, except in cases of extreme negligence. If individuals were to be punished every time a near miss occurs, the system would simply not be used. The reporting system must be simple to use and must require as little effort as possible to submit. There must also be some type of feedback system in place.

Dummy (for references Lock 2011)