NEBOSH International Diploma

UNIT IA
International Management of Health and Safety

Sample Trainer Pack

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reference only.
• A ‘helicopter’ plan (MS Word) – an overview of how the course will be delivered over its duration.
• Daily lesson plans (MS Word) – a suggested breakdown of how the detailed subjects specified in the qualification
syllabus will be covered on each day of the course
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Approx.
Timing
Content and Tutor Activity
Day 3
Aids and Equipment

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Student Activity

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0900-0930 Review answers to questions from previous evening directed private Flip chart Whole group feedback on
study answers

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Review day 3 course content
IA2 - LOSS CAUSATION AND INCIDENT INVESTIGATION

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IA2.1 Theories of loss causation

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Accident causation models PowerPoints and flip chart Listening and responses to
Accident ratio studies group directed Q&A and
Latent and active failures – Reason’s model of accident causation general discussion (with

Supplemented with V.E, Q&A and discussions

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accident scenarios contributed
by students)

1045-1100 Break

Injury rate calculations

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IA2.2 Quantitative analysis of accident and ill-health data

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Application of statistical and epidemiological methods.
PowerPoints and flip chart Listening and responses to
group directed Q&A and

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Presentation and interpretation of loss event data general discussion

Example calculations, V.E, Q&A and discussions

1245-1315 Lunch
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IA2.3 Reporting and recording of loss events (injuries, ill-

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health and dangerous occurrences) and near misses

Reporting and recording of loss events and near misses – including

discussion of how accidents are recorded in students’ workplaces.
PowerPoints and flip chart Listening and responses to
group directed Q&A and

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general discussion

RRC International
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Small group exercise
Case study (accident reporting - resource 1). Use qu. 1 - review the Case study (question and answer) and Discuss case in pairs/small
suitability of the accident report form. flip chart to capture group discussion groups and feedback to group

1500-1515 Break
1A2.4 Loss and near miss investigations
findings

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as a whole

Investigation of loss events, including reference to use of failure

tracing methods (discussed in detail in element A3) – V.E. with Q&A
and also discussion of how students investigate workplace accidents
(employers’ systems)
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PowerPoints and flip chart Listening and responses to
group directed Q&A and
general discussion

1650-1700 End of session summary and close

Directed Private Study Set
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Read through today’s handout notes. Attempt revision questions for
IA2.
Review day 4 course content

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From the ILO website, download a copy of the ILO code of practice
on reporting accidents and familiarise self with basic requirements

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RRC International
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Environmental
NEBOSH International Diploma
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Element IA2: Loss Causation and Accident
Diploma L E
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Investigation
Learning Outcomes as per Syllabus Guide

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© RRC International
 Element IA2
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Theories of Loss Causation
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 Accident Data - Ratio Studies
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1 Serious Injury

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F.E. Bird
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Minor Injury

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600 M A
Damage Only

Near-Miss

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UK Accident
Heinrich
Major or LTA
Data

S A 1 Fatal

Major
1

29 Minor

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400 > 3-day LTA

300 No injury

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© RRC International
 Single Cause “Domino” Theories
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Heinrich
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Applicable to simple accidents

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 Bird and Loftus - Modification of Heinrich's
Theory
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 Multi-Causality Theories (more complicated
accidents)
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LOSS CAUSATION AND INCIDENT

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ELEMENT

INVESTIGATION 2

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LEARNING OUTCOMES

On completion of this element, you should
be able to demonstrate understanding

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of the content through the application
of knowledge to familiar and unfamiliar
situations and the critical analysis and
evaluation of information presented in
both quantitative and qualitative forms. In
particular you should be able to:

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 Explain
 theories of loss causation.

 Explain the quantitative analysis of accident/incident

and ill-health data, limitations of their application,
and their presentation in numerical and graphical
form.

 Explain the external and the internal reporting and

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recording systems for loss events (injuries, ill health,
dangerous occurrences) and near misses.

 Explain loss and near-miss investigations;

the requirements, benefits, the procedures,
the documentation, and the involvement of
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and communication with relevant staff and

representatives.
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© RRC International Unit IA – Element IA2: Loss Causation and Incident Investigation | 2-1
Contents

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THEORIES OF LOSS CAUSATION 2-3
Accident/Incident Ratio Studies 2-3
Domino and Multi-Causality Theories 2-4
Immediate, Underlying and Root Causes 2-7
Reason’s Model of Accident Causation 2-8
Revision Questions 2-9

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QUANTITATIVE ANALYSIS OF ACCIDENT AND ILL-HEALTH DATA 2-10
Calculating Loss Rates from Raw Data 2-10
Statistical and Epidemiological Analyses in the Identification of Patterns and Trends 2-11
Presenting and Interpreting Loss Event Data 2-11

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Principles of Statistical Variability, Validity and the Use of Distributions 2-15
Revision Question 2-16

REPORTING AND RECORDING OF LOSS EVENTS (INJURIES, ILL HEALTH, DANGEROUS OCCURRENCES) AND
NEAR MISSES 2-17
Reporting Requirements and Procedures 2-17

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Internal Reporting and Recording 2-19
Revision Questions 2-27

LOSS AND NEAR-MISS INVESTIGATIONS 2-28

Purposes of Accident Investigation 2-28
Investigation Procedures and Methodologies 2-30
Communications Focusing on Remedial Actions and Lessons Learnt 2-34
Use of Failure Tracing Methods as Investigative Tools 2-34
Revision Questions 2-34
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SUMMARY 2-35

EXAM SKILLS 2-37

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2-2 | Unit IA – Element IA2: Loss Causation and Incident Investigation © RRC International
 Theories of Loss Causation

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KEY INFORMATION
• Incident studies have demonstrated that in any organisation there is a relationship between the number of major
incidents and those with less serious outcomes.
• The Single Cause Domino Theory suggests that in an accident there is a sequence of events or circumstances that

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precede the harm, i.e.
–– Ancestry (i.e. upbringing).
–– Fault.
–– Unsafe act.

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–– Accident.
–– Injury.
• Multi-causal theories suggest that preceding an incident there is a combination of causal factors at each level that
may combine to lead to the loss event.
• Reason’s model of organisational accidents states that for a major accident to occur a series of defences must be

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defeated for the hazard to lead to a loss event. Unsafe acts may cause the failure of the defences. Unsafe acts are
made more likely by local conditions in the workplace.

Other researchers have produced similar accident ratio

triangles:
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ACCIDENT/INCIDENT RATIO STUDIES

There is no shortage of data on incidents such as accidents
or near misses. Some researchers have studied the
figures in detail and concluded that there appears to be
Labour force survey 1990
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a relationship between the numbers of different types of

accident.
F. E. Bird used accident data to produce the following
accident triangle:
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Bird’s accident ratio triangle UK accident data

© RRC International Unit IA – Element IA2: Loss Causation and Incident Investigation | 2-3
Theories of Loss Causation

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DOMINO AND MULTI-CAUSALITY THEORIES
One of the duties of the safety practitioner is to keep
details of accidents and ill-health conditions and carry
out investigations. The law requires certain accidents
and occupational diseases to be reported. Often the
information that is recorded at the time of an accident

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is not adequate for the purpose of investigation into the
cause, and so is certainly inadequate for the purpose of
preventing the accident happening again.
For example, the report form may ask for the nature and
cause of the injury. This could be written as:

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Heinrich’s accident triangle • Nature of injury - cut finger.
The actual figures vary between the different accident • Cause of injury - caught on a sharp piece of metal.
triangles, but the important thing to note is that for every
The safety practitioner needs to know a lot more than this
major incident or fatality, there are many more less serious
such as:
or near-miss incidents.

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• Which finger?
Analysis also shows that:
• How serious was the cut?
• It is invariably a matter of chance whether a given event
results in injury, damage, or a near miss, i.e. near misses • Was this part of the normal job?
could so easily become more serious incidents. • Should it have been sharp?
• Near-miss/less-serious incident data can, therefore, be • Should it have been there?
a useful predictor of accident potential.
• How should it have been handled?
• All events are due to failure to control – so we can
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learn from even minor incidents. A good starting point in investigations is to consider the
two basic theories for accident causation.
The data from these triangles has a number of limitations
that you need to think about before trying to apply it: Note that domino theory presents a simplified model,
which considers only one cause of an accident. Also, in
• Not every near miss or minor incident involves risks the Heinrich model, the focus is on immediate rather than
which could actually have led to a serious incident or root causes. Both models are highly reactive and cannot be
fatality.
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used to predict the likelihood of accidents.

• Be careful comparing:
–– Different triangles. Single Cause Domino Theory
–– Different definitions (e.g. lost-time accidents). According to Heinrich:
–– Different industries (with different types of risk). “A preventable accident is one of five factors in a
• Statistical significance – you need a certain amount sequence that results in an injury. The injury is
invariably caused by an accident and the accident in
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of representative data for a meaningful comparison

between your workplace and industry as a whole. turn is always the result of the factor that immediately
precedes it.”
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 Theories of Loss Causation

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The five factors in Heinrich’s accident sequence are If this sequence is interrupted by the elimination of even
summarised in the following table. one of these factors, the injury cannot occur and the
accident has been prevented. In the case of the accident
Heinrich's accident sequence
sequence, perhaps the easiest factor to eliminate is
Accident Factors Description Number 3, the “unsafe act and/or mechanical or physical
1. Ancestry and Recklessness, stubbornness, hazard”.

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social environment greed and other undesirable
traits of character that may
be passed along through
inheritance. Environment may
develop undesirable traits of

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character or may interfere with
education. Both inheritance and
environment may cause faults of
person.
2. Fault of person Inherited or acquired faults
of person such as recklessness,
violent temper, nervousness,

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excitability. These constitute
reasons for committing unsafe
acts or for the existence of
mechanical or physical hazards.
3. Unsafe act and/ Unsafe performance of persons
or mechanical or such as: standing under danger
physical hazard areas, careless starting of
machines, removal of safeguards
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and horseplay; mechanical
or physical hazards such as
unguarded gears or points of
operation, insufficient light, which
result in accidents.
4. Accident Events such as falls of persons,
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striking of persons by flying

objects, etc. are typical accidents
which cause injury.
5. Injury Fractures, lacerations, etc. are
injuries which result directly from
accidents.
The major point that Heinrich makes is that a preventable
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injury is the natural culmination of a series of events or

circumstances which occur in a fixed logical order. Here an
analogy can be made with a row of dominoes placed on
end, such that if one falls it will cause the next to fall and
so on throughout the series (see figure that follows). If
one of the dominoes is removed, the chain of events will
be halted. In the same way, consider Heinrich’s accident
sequence:
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1. Ancestry and social environment.

2. Fault of person.
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3. Unsafe act and/or mechanical or physical hazard.

4. Accident.

5. Injury.

© RRC International Unit IA – Element IA2: Loss Causation and Incident Investigation | 2-5
Theories of Loss Causation

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Bird and Loftus extended Heinrich’s theory to take into
account the influence of management in the cause and
effect of accidents, suggesting a modified sequence of
events:
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Heinrich’s domino sequence

Usually simple accidents have a single cause, which is why

such events so frequently occur; but the consequences
tend to be of a minor nature. A major disaster normally has
multiple causes, with chains of events, and combinations of
events. Fortunately, they are rare occurrences.
1. Lack of control by management.
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The multi-causal model considers that there may be
2. This permits the existence of basic causes (i.e. personal organisational, cultural, managerial, etc. causes that
and job factors). interact and result in an accident. The model is more
complex than the single-cause domino theory and can
3. In turn, this leads to immediate causes (such as sub- be used not only for accident investigation, but also to
standard practices, conditions or errors). prevent accidents if the outcomes of monitoring activities
are analysed. The model can also be linked to more
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4. These are subsequently the direct causes of the acci-

dent. advanced analysis techniques, such as fault trees and event
trees. The downside is that they are more complex and
5. Finally, this results in loss (which may be categorised as therefore take longer to carry out.
negligible, minor, serious, or catastrophic).
This modified sequence can be applied to every accident Systems Theory
and is of basic importance to loss-control management. This is another way of looking at a multiple cause situation.
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Factories and processes can be viewed as systems, i.e. an

Multi-Causal Theories assembly of parts or components connected together
There may be more than one cause of an accident, not in an organised way to perform a task, with inputs and
only in sequence, but occurring at the same time. For outputs, and various kinds of control mechanisms.
example, a methane explosion requires: A systems approach is often useful in simplifying complex
• Methane in the explosive range of 5% to 15%. operations. Part of the system can be taken as a ‘black box’,
with only the inputs and outputs considered.
• Oxygen, or air.
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System failures are prevented or minimised by

• Ignition source.
components which cannot fail, by backup systems, or
The ignition will only happen if these three events occur by redundancy built into the system (see Element IA4).
together. Each of the three events may, in themselves, Accidents happen in our system because it includes fallible
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be the end result of a number of different sequences components such as machines and human beings. The
of events. In accident investigation, all causes must be system is operating in the failure mode.
identified.
You can see the essential features of the multiple causation
approach in the following figure.

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 Theories of Loss Causation

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Features of the multiple causation approach

IMMEDIATE, UNDERLYING AND ROOT An unsafe act is human performance that is contrary to
accepted safe practice and which may, of course, lead to an
CAUSES
accident. Unsafe conditions are basically everything else
There are various ways of classifying accident causes. that is unsafe after you take away unsafe acts. So, this is
Remember that the same term may be used by different the physical condition of the workplace, work equipment,
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people to mean different things – you can check this for the working environment, etc. which might be considered
yourself by doing an Internet search on the above terms. unsafe and could therefore foreseeably lead to an accident
When analysing accidents it is common to distinguish if not dealt with.
between immediate causes and underlying causes. The Note that an unsafe act or unsafe condition alone could
latter are also sometimes called root causes. The term result in an accident. For example, “messing around” is
used can vary, but the most important thing to remember an unsafe act which could take place in otherwise safe
is to look beyond the symptoms of the accident. You need conditions, but could nevertheless result in an accident.
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to dig down beyond the obvious (immediate) causes to Similarly, a person could be working in a perfectly safe
discover why it happened, or why it was allowed to happen. manner, using safe equipment and materials, but suffer
Usually, an accident occurs as a result of multiple chains of injuries as the result of the collapse of a floor affected by
events; following these back will lead to underlying causes, severe woodworm and dry rot. (You could argue, however,
tackling which can stop similar accidents happening again. that collapse of the floor was due to an unsafe act, i.e.
• Immediate cause refers to the direct cause of the failure to inspect the floor and supporting joists and to
accident, i.e. the actual agent of injury or damage, such calculate the floor loadings.)
as the sharp blade of the machine. According to the accident sequence we discussed earlier,
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• Underlying, or root causes are the less obvious unsafe acts and conditions are caused only by faults of
systemic, or organisational reasons for the incident. persons, and these faults are created by the environment,
or are acquired by inheritance.
We will now look at unsafe acts and conditions in more
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detail. The faults themselves generally arise because of

inappropriate attitudes, lack of knowledge or skill, or
physical unsuitability.

© RRC International Unit IA – Element IA2: Loss Causation and Incident Investigation | 2-7
Theories of Loss Causation

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REASON’S MODEL OF ACCIDENT
CAUSATION TOPIC FOCUS
However the barriers are not perfect and can be
TOPIC FOCUS defeated.
Active failures are one cause for the barriers to be

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Latent and Active Failures defeated.
Rather than using the words “immediate”, Active failures are those unsafe acts which have
“underlying” or “root” causes, the terms “latent” immediate effects on the integrity of the system
and “active” failures are also commonly used. and are usually committed by those directly involved

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Following research into a series of disasters, in the task. Such individuals often suffer directly as
James Reason (an occupational psychologist) a result of the incident and may often be blamed
has developed a model of accident causation for as well. The cause of the failure will be due to an
organisational accidents. An organisational accident error (accidental) or a violation (deliberate). Such
is rare, but if it happens it often has disastrous unsafe acts occur regularly, but few will cause the
consequences (e.g. Piper Alpha, North Sea, 1988). defences to be penetrated, an example being the
Reason’s model shows that organisational accidents chemical plant operator who opens a valve allowing

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do not arise from a single cause but from a a hazardous substance to escape.
combination of active and latent failures. The model then shows that the local workplace
factors influence the chance of an unsafe act
occurring. In the case of the hazardous substance
escape, this may be due to a lack of supervision
or training, maintenance failure, unworkable
procedures, etc.
According to the model the local workplace factors
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are affected by decisions made at a strategic
level by senior management, government,
regulators, manufacturers, etc. In the case of senior
management this might be lack of recognition of the
importance of occupational health and safety, which
will be reflected in the culture of the organisation
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by the behaviour that is considered acceptable. The

management may give safety a low priority with no
commitment and minimal funding. These failures
at the strategic levels, both in the organisation and
the external environment, are described as latent
failures because they remain dormant and possibly
unrecognised until they interact with the local
factors and the unsafe acts and work environments,
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Adapted Version of Reason’s Model of Accident Causation and increase the likelihood of an active failure.
When the gaps created by active failures align
In the model there is a series of defence barriers with those created by the latent conditions, the
between the hazard and a major incident. These opportunity exists for a serious outcome.
not only prevent the incident, (e.g. containment
of the hazard, safe operating procedures, etc.) but
also provide warning of danger (e.g. an alarm)
and mitigate the consequences (e.g. means of
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escape). These multiple layers characterise complex

technological systems such as a chemical plant.
(Continued)
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 Theories of Loss Causation

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Categories of Unsafe Acts
Unsafe acts of persons may be categorised under the
following headings:
• Operating without authority.
• Operating or working at an unsafe speed.

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• Making safety devices inoperative.
• Using unsafe equipment, or using equipment unsafely.
• Unsafe methods, e.g. loading, carrying, mixing.

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• Adopting an unsafe position or posture.
• Working on moving or dangerous equipment.
• “Messing/playing around”, e.g. distracting, teasing,
startling.
• Failure to wear safe clothing or personal protective

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devices.
• Lack of concentration; fatigue or ill health.
From this list you can see that unsafe acts may either
be deliberate violations (sometimes called ‘active’) or
unintentional errors (sometimes called ‘passive’). We
discuss these ‘human factors’ in detail in Element IA7.

Categories of Unsafe Conditions

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The following categories describe unsafe conditions from
which an accident may result:
• Inadequate guarding; guards of inadequate height,
strength, mesh, etc.
• Unguarded machinery, or the absence of the required
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guards.
• Defective, rough, sharp, slippery, decayed, cracked
surfaces.
• Machines/tools designed with insufficient attention to
safety.
• Unsafe arrangements, poor housekeeping, congestion,
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blocked exits.
• Inadequate lighting, glare, reflection.
• Inadequate ventilation, contaminated air. REVISION QUESTIONS
• Unsafe clothing - no goggles, gloves or mask. 1. Outline the five factors in Heinrich’s accident
• Unsafe processes - mechanical, chemical, electrical, sequence.
nuclear. 2. How does Bird and Loftus’ theory of accident
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• Hot, humid or noisy environment. causation differ from Heinrich’s?

3. According to Reason, what in an organisation are

“latent failures”?
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4. What important principle of accident causation

theory do accident ratio studies illustrate?
(Suggested Answers are at the end.)

© RRC International Unit IA – Element IA2: Loss Causation and Incident Investigation | 2-9